A Practical Approach to the Ultrasound Characterization of Adnexal

Transcription

CORE CURRICULUM
IN SONOGRAPHY
CME ARTICLE
A Practical Approach to the Ultrasound Characterization
of Adnexal Masses
Douglas L. Brown, MD
Abstract: Because pelvic ultrasound is commonly used to evaluate
adnexal masses, it is important to understand the most useful
sonographic features for predicting benign and malignant masses.
Determining whether an adnexal mass is of ovarian or extraovarian
origin is key in arriving at the most likely diagnosis. Most adnexal
masses are benign, and each of the most common benign ovarian
lesions has a typical sonographic appearance. Additionally, most
malignant ovarian neoplasms have a solid component with
detectable flow by Doppler ultrasound, allowing one to strongly
suggest the diagnosis. We will review an approach to the ultrasound
diagnosis of adnexal masses that progresses through a series of
4 questions to help lead one to the most likely diagnosis.
Key Words: ovary, adnexa, neoplasm, cancer, Doppler
(Ultrasound Quarterly 2007;23:87Y105)
LEARNING OBJECTIVES
1. Describe the most predictive ultrasound features of the
5 most common benign ovarian masses.
2. Identify the sonographic features most predictive of
ovarian malignancies.
3. Describe a systematic ultrasound approach to determine
the most likely diagnosis for an adnexal mass.
P
elvic ultrasound is frequently the first imaging modality
used when abnormalities are suspected of the ovaries or
adnexa. It is incumbent on sonographers and physicians who
perform and interpret pelvic ultrasound to understand the
most useful sonographic features. It is of little use to our
patients or referring physicians to give an exceedingly long
differential diagnosis or report a mass as just a Bcomplex
cyst^ without further description or characterization. Most
adnexal masses are benign, and we now have enough
accumulated ultrasound knowledge to confidently recognize
most benign adnexal masses. Many adnexal masses have such
a typical ultrasound appearance that a reasonably confident
Received for publication December 29, 2006; accepted March 16, 2007.
Professor of Radiology, Mayo Clinic, Department of Radiology, Rochester,
MN.
Dr Brown has disclosed that he has no financial interests in or relationships
with any commercial companies pertaining to this educational activity.
Lippincott Continuing Medical Education Institute, Inc. has identified and
resolved all faculty conflicts of interest regarding this educational activity.
Reprints: Douglas L. Brown, MD, Mayo Clinic, Department of Radiology, 200
First St, SW, Rochester, MN 55905 (e-mail: [email protected]).
Copyright * 2007 by Lippincott Williams & Wilkins
Ultrasound Quarterly
diagnosis can be made by ultrasound.1 Using the power of this
knowledge will serve our patients well by allowing for more
conservative management when appropriate and decreasing
patient and physician anxiety. Most malignant masses can
also be recognized by ultrasound. There will be occasional
problematic cases, but we can serve our patients best by
knowing the common and predictive sonographic appearances of both benign and malignant adnexal masses.
In this article, we will review a practical approach to the
ultrasound diagnosis of adnexal masses. This approach
progresses through a series of 4 general questions in an
attempt to arrive at the most likely diagnosis. Those 4
questions are the following:
1. Is the adnexal mass extraovarian in origin?
2. If the mass is ovarian in origin, is it one of the BBig 5^?
3. Does the clinical history help?
4. Is it a complex cystic mass, or is it a solid mass?
There admittedly will be cases that remain problematic
after this or any approach, but they are infrequent.
Occasionally, other imaging modalities such as computed
tomography (CT), positron emission tomography, or magnetic resonance (MR) scanning can be helpful. Magnetic
resonance, in particular, has a role in the characterization of
so-called indeterminate adnexal masses.2 However, it is my
view that the designation of a mass as indeterminate is
variable and inconsistent, with the potential to designate too
many masses as indeterminate if the interpreting physician is
not actively involved in evaluating these masses. I believe
that the number of seemingly Bindeterminate^ adnexal
masses will be minimal if one is aware of the sonographic
features to be discussed here.
IS THE ADNEXAL MASS EXTRAOVARIAN
IN ORIGIN?
Although most adnexal masses arise from the ovary,
diagnostic errors will be made if one assumes an adnexal
mass is of ovarian origin. It is important to try to make the
distinction of ovarian versus extraovarian origin during the
real-time scan. Seeing ovarian tissue with follicles extending
around the mass will help confirm an ovarian origin in the
premenopausal patient. Ovarian origin may be more difficult
to determine with large masses or in the postmenopausal
patient with a small ovary without follicles. Recognition of an
ipsilateral ovary separate from the mass allows for ready
determination of an extraovarian origin. The most problematic cases occur when no ovarian tissue is seen around the
mass or separate from the mass. In such cases, the origin may
& Volume 23, Number 2, June 2007
Copyright @ Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.
87
Brown
not be clear, and one may need to consider both ovarian and
extraovarian causes. Occasionally, in these cases, the mass
has features typical of, for instance, a dermoid or a
hydrosalpinx that will allow one to suggest the likely
diagnosis even without knowing the origin of the mass for
certain.
Although one cannot always distinguish ovarian from
extraovarian origin, there are a few things that can be done
during the scan to increase the likelihood of making this
distinction. During transvaginal scanning, gentle pressure
with the transvaginal transducer and/or with a hand on the
patient’s abdomen may be useful. When some ovarian tissue
is seen immediately adjacent to an adnexal mass, such
pressure may help to separate the two in cases of an
extraovarian mass. Additionally, one should look with a
transabdominal transducer, even if the bladder is empty, as
this might reveal a separate ovary superiorly or laterally in the
pelvis. Another feature that may be useful is the vascular
supply of the lesion. This is most likely to be helpful with
pedunculated fibroids. If one can show vessels bridging
between the uterus and the solid adnexal mass, then a
pedunculated fibroid is likely.3,4
Most extraovarian adnexal masses are benign.5 Several
extraovarian masses have characteristic features that allow
one to make an accurate diagnosis. Table 1 lists some
extraovarian masses that one may encounter. It is not an allinclusive list, and the designations of common versus
uncommon and typical imaging appearance may be open to
debate. We will consider several of the more common
extraovarian masses listed in Table 1.
FIGURE 1. Paraovarian cyst. Image from a transvaginal
ultrasound of the right adnexa reveals a simple cyst (between
arrows). The cyst is adjacent to, but separate from, the right
ovary (O).
Paraovarian Cyst
It is not unusual to encounter a paraovarian or paratubal
cyst during a pelvic sonogram.6 The term paraovarian cyst
will be used here, realizing that one cannot typically
determine exactly where they arise by ultrasound, and the
distinction does not seem to be clinically important. These
typically appear as simple cysts by ultrasound (Fig. 1) and are
indistinguishable from ovarian cysts if one does not recognize
the extraovarian location.7,8 Occasionally, paraovarian cysts
have internal echoes due to hemorrhage.9
Paraovarian Cystadenoma
TABLE 1. Causes of Extraovarian Masses in the Female Pelvis
Predominately cystic masses
Common
Uncommon
Predominately solid masses
Common
Uncommon
Variable sonographic appearance
Common
Uncommon
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Paraovarian cyst
Hydrosalpinx
Peritoneal inclusion cyst
Paraovarian cystadenoma
Tarlov cyst
Bladder diverticulum
Lymphocele
Abscess
Varices
Paraovarian cystadenomas or cystadenofibromas
(Fig. 2) are uncommon but should be considered when an
extraovarian cyst contains a mural nodule or septation.6,10,11
Malignancy is rare in such lesions, although they are often
removed surgically. This seems to be the same lesion
histologically that occurs with increased frequency in the
epididymis of men with von Hippel-Lindau syndrome.12,13
Pedunculated fibroid
Neural neoplasms
Lymphadenopathy
Rudimentary horn of unicornuate uterus
Tubal pregnancy
Fallopian tube neoplasm
Gastrointestinal tract lesions
Neoplasms
Appendiceal mucocele
Appendicitis
Meckel diverticulum
Distended iliopsoas bursa
FIGURE 2. Paraovarian cystadenoma. Image from a
transvaginal ultrasound shows cystic mass with a nodular solid
component (arrow). The ipsilateral ovary (not shown) was
separate from the cystic mass.
* 2007 Lippincott Williams & Wilkins
Ultrasound Characterization of Adnexal Masses
Hydrosalpinx
A hydrosalpinx should be considered when one
encounters an elongated cystic mass with a tubular shape14
that is not a vessel (Fig. 3A). Incomplete septations (Fig. 3B),
which, in a hydrosalpinx, likely represent the wall of the
distended tube as it folds on itself, were initially reported to
be a reliable indicator of a hydrosalpinx.15,16 A recent study,
however, found that an incomplete septation, although more
common in hydrosalpinges than in other lesions, was not a
reliable discriminator.17 That study found the waist sign,
defined as indentations along opposite sides of the cystic
mass, to be the most discriminating ultrasound feature of a
hydrosalpinx (Fig. 3C).17 One may also encounter small
nodular-appearing areas along the wall of a hydrosalpinx
(Fig. 3B), referred to as Bbeads-on-a-string^ which are probably due to abnormal endosalpingeal folds.16
One should be careful not to mistake small tortuous
veins with slow flow for a hydrosalpinx. The flow may be so
slow that it is not detectable by Doppler techniques, and thus,
one might assume that it is a hydrosalpinx. Increasing the
gray scale gain slightly and looking for movement of lowlevel echoes in the lumen will help one recognize such veins
with slow flow.
Fallopian tube carcinoma is rare tumor18 and is an
uncommon exception to the rule that extraovarian adnexal
masses are benign lesions. It should be considered if one
encounters a solid mass or papillary projections within an
extraovarian tubular cystic mass (Fig. 4).19,20 It may rarely
be difficult to distinguish such a solid component that is
worrisome for a tubal carcinoma from the projections
described as Bbeads-on-a-string^ in a chronic hydrosalpinx.
In my experience, the nodular areas in a chronic hydrosalpinx seem to be smaller and multiple, whereas the solid
component in a fallopian tube neoplasm is larger and often
is solitary.
Peritoneal Inclusion Cyst
The peritoneal inclusion cyst (PIC) has also been
referred to by other terms, including peritoneal pseudocyst
FIGURE 3. Hydrosalpinx. A, Image from a transvaginal
ultrasound reveals a tubular cystic mass with a partial septation
(arrow). A normal ovary (not shown) was seen separate from
the mass. B, Image from a transvaginal ultrasound in a different
patient. This hydrosalpinx contains a partial septation
(arrowheads) and multiple small nodular areas (arrows) along
the wall because of thickened endosalpingeal folds. If one did
not recognize that this lesion was extraovarian in location, it
could be mistaken for an ovarian carcinoma. C, Image from a
transvaginal ultrasound in another patient with hydrosalpinx
reveals a tubular cystic mass with the ‘‘waist sign’’ (arrows).
The calipers mark the adjacent ovary.
However, it seems uncommon in women, and the strength of
its association with von Hippel-Lindau syndrome in women
is not clear.
FIGURE 4. Transvaginal ultrasound with color Doppler
ultrasound image (shown in grayscale) of the left adnexa
shows a solitary, relatively large, solid mass (M) within a dilated
fallopian tube (between arrows). Flow was detected within the
solid component.
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Tarlov Cyst
Tarlov cysts, also referred to as perineural or root sleeve
cysts, are uncommon, but it is important to recognize them
because they can be mistaken for gynecologic pathology and
treated inappropriately. Patients could potentially undergo
unnecessary or harmful surgery if these are not recognized.
Most Tarlov cysts are asymptomatic and discovered incidentally.26 Rarely, surgery may be performed if they are felt to be
the cause of pain.26
Tarlov cysts may be unilateral or bilateral. Small Tarlov
cysts are not typically seen by ultrasound, and it is usually the
larger cysts that are seen sonographically. Tarlov cysts almost
always have internal echoes,27Y29 although it is not clear what
these echoes represent (Fig. 6). The cysts tend to appear as
slightly elongated or beaded cystic masses posteriorly. This
might present some confusion with a hydrosalpinx, but
Tarlov cysts do not tend to be as elongated and tubular as a
hydrosalpinx, although this admittedly is a subjective
evaluation that may be difficult. One would also probably
not expect to see an incomplete septation or Bwaist sign^ in a
Tarlov cyst. Computed tomography or MR can be used to
confirm the diagnosis of a Tarlov cyst and readily shows their
origin from sacral neural foramina.
FIGURE 5. Peritoneal inclusion cyst. A, Transverse image from
a transabdominal ultrasound of the pelvis shows cystic mass
with septations (arrows). B, Image from a transvaginal
ultrasound in the same patient shows normal ovary (between
arrows) at the edge of the cystic mass (labeled C), with the
mass extending around the ovary. U indicates uterus.
and inflammatory cyst of the peritoneum. It is thought to be
caused by peritoneal adhesions that trap fluid produced by a
functioning ovary. Most patients have a history of prior pelvic
surgery, endometriosis, or pelvic inflammatory disease (PID)
that results in pelvic adhesions.
Several articles have described the ultrasound appearance of PICs.21Y25 The ovary typically appears to be inside the
PIC by sonography, often at the periphery of the cyst. Most
PICs have septations. In 1 study, gentle pressure with the
transvaginal transducers showed movement of the septations
in 48% of PICs.25 Such mobility of septations has been
suggested as more common in PICs than in neoplasms25;
however, to my knowledge, this has not been confirmed in
other studies. The fluid is typically anechoic, but there can be
internal echoes. Peritoneal inclusion cysts may have bizarre
shapes25 and sometimes conform to the shape of the
surrounding structures, a feature which may be more evident
on CT or MR scanning. Thus, when one encounters a septated cystic pelvic mass in a patient with a history of pelvic
surgery, endometriosis, or PID, a careful search should be
made for a normal ovary within or at the periphery of the
cystic mass (Fig. 5).
90
FIGURE 6. Tarlov cysts. A, Transverse transabdominal
ultrasound image reveals 3 adjacent cystic masses posteriorly
on the left. B, Transvaginal ultrasound image of one of the
posterior left adnexal masses in the same patient reveals
internal echoes within the cystic mass (between arrows). The
left ovary (not shown) was seen separate from all 3 lesions.
B indicates bladder; U, uterus.
IF THE MASS IS OVARIAN IN ORIGIN, IS IT ONE
OF THE BIG 5?
Once one has confirmed an ovarian origin of the mass,
the most common lesions need to be considered. Most ovarian
masses encountered in clinical imaging practices are benign.
Simple cysts, hemorrhagic cysts, corpora lutea, endometriomas, and dermoids are likely to be the most frequent ovarian
masses that one will encounter. I refer to these as the BBig 5^
because they are so common and usually have a typical
ultrasound appearance that allows one to make a confident
diagnosis. A small percentage of these lesions will not have
the classic appearance. In such cases, knowledge of the more
frequent atypical findings will allow one to favor a particular
diagnosis, although with a lesser degree of confidence than
when the lesion has the classic appearance.
Simple Cyst
An ovarian follicle typically reaches a mean diameter
of 20 to 24 mm (range, 17Y27 mm) at the time of
ovulation.30,31 Although follicles technically are simple
cysts, I believe it is better to refer to them as Bfollicles^
rather than Bcysts^ because the latter has potential to be
misinterpreted as something that may be abnormal or need
follow-up.32 Thus, I would generally consider a simple cyst
less than about 25 mm in mean diameter to be normal in the
ovary of a premenopausal woman. A simple cyst in the ovary
should meet the same criteria as a simple cyst in any organ:
anechoic, thin wall, and distal acoustic enhancement.
As many ovarian simple cysts (Fig. 7) will resolve, the
cause is not often proven. Many are probably follicular cysts.
A small percentage of corpus luteal cysts are simple cysts by
sonography.33 Serous cystadenoma can appear as a simple
cyst and is a more likely consideration with simple cysts that
are large and those in older patients. The approach to followup of simple ovarian cysts in premenopausal women is not
standardized. It has been suggested that simple cysts of less
than 3 cm do not require followup.34
FIGURE 7. Simple ovarian cyst. Transvaginal ultrasound
images shows a simple cyst (labeled C) arising from the right
ovary.
Simple ovarian cysts occur in 3.5% to 17% of
postmenopausal women.35 On follow-up ultrasound, most
such cysts either disappear or remain stable.36Y39 Only a small
percentage, generally less than approximately 10%, increase
in size.36Y39 In many lefts, a simple cyst that remains less than
5 cm in size is managed with follow-up ultrasound.34,40Y42 If
the cyst becomes larger than 5 cm or changes appearance,
surgery is usually warranted.34,41 Of those cysts treated
surgically, the majority are serous cystadenomas.42
This brings up the question of the frequency of
malignancy in a simple ovarian cyst. We generally assume
that this is uncommon, although there are occasional reports
of malignancy in simple ovarian cysts.43Y45 These were
typically older studies using transabdominal transducers, or
the sonographic methods were not always clear. In a more
recent study of a large number of cases with well-defined
methods and use of transvaginal scanning, the frequency of
malignancy in simple ovarian cysts was 0.7% in premenopausal women and 1.6% in postmenopausal women.40
Interestingly, all malignancies occurred in cysts of larger
than 7.5 cm in mean diameter. Pathologically, there were
usually small mural nodules that were not seen sonographically. Therefore, for cysts that are well seen with transvaginal
scanning (and also with transabdominal scanning when
needed for larger cysts), the likelihood of malignancy in
simple cysts of less than 7.5 cm is virtually nil. The authors
suggested that the 5-cm threshold for conservative versus
surgical management remains valid.40 Thus, we should
recognize that, for larger cysts, there is a slight chance that
small nodular areas along the cyst wall can be missed,
probably because of the larger surface area to be evaluated.
Sonographers and sonologists should carefully scrutinize the
entire inner cyst wall in these lesions.
Hemorrhagic Cyst
Hemorrhagic cysts occur commonly in the ovaries of
premenopausal women. The patient may present for medical
care because of acute pain. A recent study found 2 particular
sonographic features to be reliable.46 Hemorrhagic cysts
often have internal echoes with a pattern of fine interdigitating lines46 that have been variously described as Breticular,^
Bfishnet,^ or Blacelike^ and are believed to be caused by fibrin
strands that result when clot hemolyzes.34,46 This reticular or
fishnet pattern (Fig. 8A) due to fibrin strands was found to
have a sensitivity of 90%, specificity of 98%, and positive
likelihood ratio (LR) of 40 for hemorrhagic cysts.46 Fibrin
strands have the potential to be confused with septations.46
However, fibrin strands tend to be very thin, rarely extend all
the way across a cyst, and arc within the cyst, as opposed to
true septations that have more substance and are hence
thicker and extend to opposite walls of the cyst in a linear
or slight curvilinear fashion. The other reliable ultrasound
feature which is retracting clot (solid echoes with a concave margin) was found to have an even higher LR (967)
and specificity (100%), but its sensitivity was only 30%
(Fig. 8B). The combination of fibrin strands, no septations,
and smooth walls was found to have an LR of 200, with
sensitivity of 90% and specificity of 100%.46 It has been
suggested that follow-up ultrasound of classic hemorrhagic
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cysts is probably not necessary unless the patient remains
symptomatic.46,47
Occasionally, hemorrhagic cysts have other appearances. In these instances, one is not likely to confidently make
the diagnosis on a single sonogram but would at least consider
the possibility and suggest a follow-up sonogram. Most
hemorrhagic cysts will resolve within 6 to 8 weeks.34,47
Infrequently, the clot may have convex outer margins and
simulate a solid area of a neoplasm (Fig. 8B). Absence of flow
in the seemingly solid area by Doppler ultrasound is
reassuring, but follow-up ultrasound is generally needed. A
minority of hemorrhagic cysts will have heterogeneous
internal echoes and seem to be solid (Fig. 8C); this likely is
caused by acute or subacute clot.47 Doppler ultrasound can be
useful to consider this possibility and not send the patient
directly to surgery for a solid ovarian neoplasm before obtaining a follow-up ultrasound. Fluid-fluid levels occasionally
occur in hemorrhagic cysts.47 In my experience, the more
echogenic fluid is located dependently in hemorrhagic cysts.
Corpus Luteum
FIGURE 8. Hemorrhagic ovarian cysts. A, Transvaginal
ultrasound image shows a complex cystic mass (between
arrows) with a reticular or fishnet pattern of internal echoes.
This is the classic appearance of a hemorrhagic ovarian cyst. B,
Transvaginal ultrasound image shows 2 hemorrhagic cysts in
the left ovary. Seemingly solid area in one of the cysts has a
concave margin (arrow), which is suggestive of clot. The other
seemingly solid area (arrowhead) did not have concave
margins. This can also occur with clot but makes it harder to
distinguish from true solid tissue of a neoplasm. Both cystic
lesions resolved on follow-up ultrasound 1 month later. C,
Transvaginal ultrasound image of a hemorrhagic cyst (between
arrows) in the acute to subacute stage. As opposed to lesion in
part A, the echoes in this cyst are more heterogeneous and
more echogenic, potentially leading one to suspect a solid
mass. Color Doppler ultrasound (not shown) showed no flow
within the lesion, and it resolved on follow-up ultrasound.
92
It is important to recognize the corpus luteum (CL) as a
normal finding in premenopausal women and not mistake it
for something more sinister. One expects to see the CL in the
secretory phase of the menstrual cycle and in the first trimester
of pregnancy. It may also be seen in the subsequent follicular
phase.48 The appearance of the CL has been described in a few
studies using transvaginal sonography.33,48,49 Unfortunately,
the ability to discriminate the CL from true abnormalities by
sonography has not, to my knowledge, been investigated.
Different schemes to describe its appearance have also been
used. Although these technically are cysts, usually complex
cysts, it has been suggested that we refer to them as a CL,
rather than a corpus luteal cyst, unless they are larger than
approximately 4 to 5 cm.32 The CL is typically less than
approximately 3 cm in diameter.49
The CL often appears as a small cystic lesion with a
crenulated wall and low-level internal echoes (Fig. 9A),34,50
although it may have a variable appearance. In a study of the
CL during the normal menstrual cycle, the majority had a
central cystic cavity.48 The minority had no such cystic
cavity48 and appeared as a hypoechoic to isoechoic area in the
ovary. Central cystic areas became less frequent with
increasing time from ovulation. The wall was described as
thickened and irregular but was not a specific feature that
was evaluated.48
In another study of the CL in early pregnancy, 34%
of patients had a CL that was hypoechoic compared with
the ovary (Fig. 9B), 27% had a thick-walled cyst with
anechoic center, 23% had a cyst with internal echoes, and
15% had a simple cyst.33 The wall is usually hypoechoic or
isoechoic compared with adjacent ovarian parenchyma.51
The isoechoic or slightly hypoechoic lesions may be
overlooked.33 In my opinion, small lesions that have one
of these typical appearances in a premenopausal patient
should be considered as the normal CL. I admit, however,
that the discriminatory ability of such features has not been
proven, and there will be some cases where one is not
reasonably certain that the lesion is a CL, and follow-up
ultrasound may be appropriate. The CL is typically a very
vascular structure, and one should not be surprised to see
abundant flow peripherally49 by color or power Doppler
ultrasound (Fig. 9C). Corpora lutea may also incidentally
be identified on CT, typically as lesions of less than 3 cm
with thick, crenulated, enhancing walls.52
Endometrioma
Ultrasound is not reliable for identifying the small
deposits of endometriosis but is useful for identifying
endometriomas.53 Although the deposits of endometrial
tissue may occur in many locations and are common on
peritoneal surfaces, endometriomas usually occur in the
FIGURE 9. Corpus luteum. A, Transvaginal ultrasound image
shows a CL (between the calipers), appearing as a complex
cystic mass with a crenulated wall and internal echoes in a
central cystic cavity. Small amount of free fluid (labelled FF) is
also present. B, Transvaginal ultrasound image in a different
patient shows a hypoechoic appearance to the CL (marked by
calipers). This can result when the internal echoes are similar in
echogenicity to the wall of the lesion. Corpora lutea with this
appearance can be overlooked because they are often similar in
echogenicity to the adjacent ovary. C, Transvaginal ultrasound
image with color Doppler ultrasound from the same patient
as in part B shows abundant flow around the periphery of
the CL (arrows). FF indicates free fluid.
FIGURE 14. Color plates for images 14A, 14B and 14C.
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ovary.54 Endometriomas (Fig. 10A) typically have homogeneous low- to medium-level internal echoes.55Y58 The
appearance of hemorrhagic cysts and endometriomas overlaps58Y60 in a small percentage of cases, but endometriomas
tend to have more homogeneous internal echoes as opposed to
the more heterogeneous and reticular pattern in hemorrhagic
cysts. This homogeneous appearance has sometimes been
referred to as a Bground glass^ appearance.1
Although diffuse homogeneous internal echoes are very
common and quite typical of endometriomas, other lesions
will occasionally have low-level internal echoes.58,61 Acoustic streaming, a technique using Doppler ultrasound to show
movement or lack of movement of the internal echoes, has
been suggested as a potential method to help distinguish
endometriomas from other lesions with internal echoes.62
Initial results seem promising because most endometriomas
are reported not to have acoustic streaming, but further
experience is needed.
Septations with resulting multilocularity are common,
occurring in 45% of endometriomas in 1 study.58 Hyperechoic
wall foci were observed in 35% of endometriomas (Fig. 10B)
and were found to be a useful feature for diagnosing
endometriomas.58 To my knowledge, no other studies have
evaluated this feature of endometriomas. Wall nodularity
(Fig. 10C) occurs in approximately 20% of endometriomas58
and is problematic because this feature typically raises
concern for a neoplasm. Color Doppler ultrasound or MR
may be helpful in such instances,58 but their value in this
situation has not been proven. It has been speculated that
these solid areas are caused by clot or fibrin.1 If so, one
would expect there to be no detectable flow by color
Doppler ultrasound. I have anecdotally seen a few cases
where the nodular area was caused by endometrial tissue, in
which case, flow may be detectable by Doppler ultrasound and
then confused for a neoplasm. At least 1 case of an
endometrioma with a nodular area containing flow has been
reported.63 Infrequently, an endometrioma may have a solid
appearance.1,34,61 In my experience, this solid appearance
(Fig. 10B) tends to occur with the more chronic ovarian
endometriomas. It is not always clear whether they are really
solid lesions or just appear that way because of older blood
products and/or fibrosis. Additionally, extraovarian deposits
of endometriosis may infrequently be large enough to be
identified by ultrasound, and such deposits tend to be
solid.54,64
When one detects a cystic mass with diffuse, homogeneous, low-level internal echoes and no nodular areas, an
endometrioma is very likely. Multilocularity and/or hyperechoic wall foci may further increase the likelihood of an
endometrioma.
FIGURE 10. Endometrioma. A, Transvaginal ultrasound
image of a typical endometrioma with homogeneous low- to
medium-level internal echoes. This lesion has 2 locules
(labeled 1 and 2). Endometriomas may be unilocular or
multilocular. B, Transvaginal ultrasound image of 3 adjacent
endometriomas in the right ovary in a different patient.
Endometriomas 1 and 2 are essentially isoechoic to the ovary
and could be mistaken for solid lesions; both of these have
small echogenic foci (arrows) along part of their periphery.
Endometrioma 3 is not homogeneous, likely because of
more recent internal hemorrhage. C, Transvaginal
ultrasound image of an endometrioma in another patient.
Homogeneous internal echoes (labeled E) are present, but
there is also a solid appearing area (arrow) that is slightly
hyperechoic compared with the internal echoes. Such
solid-appearing areas are probably caused by a clot or a focal
area of endometrial tissue.
94
Mature Cystic Teratoma
Mature cystic teratomas, often referred to as dermoids,
are the most common ovarian neoplasm.34,65 Most dermoids
have one of several typical sonographic findings, allowing a
confident diagnosis by ultrasound. Most dermoids can be
accurately characterized by ultrasound.66 For the rare case
where one is not sure if it has typical sonographic features of a
dermoid, CT or MR can be performed. Either imaging
modality should allow easy recognition of macroscopic fat
and confirm the diagnosis of a dermoid. My personal view is
that MR is generally the better alternative imaging modality.
If there is no macroscopic fat, CT typically provides little in
the way of further clues to the diagnosis. Endometriomas,
however, are one of the more common false positive
diagnoses for dermoid, and MR will often allow a confident
diagnosis of an endometrioma. It is also important to note that
most dermoids do not have detectable flow within the lesion
by color Doppler ultrasound. As dermoids are prone to
torsion, it is important to assess for flow in some adjacent
normal ovary rather than in the dermoid itself when torsion
of a dermoid is being considered.
A hyperechoic area (Fig. 11A), particularly one that
attenuates sound (Fig. 11B), is a common sonographic finding
in dermoids. This feature is believed to be caused by a
mixture of hair and sebum.1,67 The terminology used to
describe this hyperechoic area is variable and includes
dermoid plug,68 Rokitansky protuberance,68 densely echogenic tubercle,69,70 echogenic nodule or mass,67,71 hyperechoic solid component,72 and regional bright echoes.66 The
Btip of the iceberg^ sign (Fig. 11B) refers to such marked
shadowing from the hyperechoic area that the deeper part of
the mass is not seen.73 The hyperechoic solid area is typically
of high echogenicity, although not as intensely echogenic as
calcification. This high degree of echogenicity is usually
obvious after one has seen typical examples, but there may be
occasional cases where one is not sure if the area is echogenic
enough to be typical of a dermoid. Magnetic resonance
should be considered in such cases. Occasionally, the entire
mass may be hyperechoic (Fig. 11C).67 The presence of distal
acoustic shadowing, often originating in the hyperechoic
area, further increases the likelihood of a dermoid.66,71 The
shadowing may have the appearance of a progressive fading
of the sound beam, probably because of a mixture of hair and
sebum, or can appear as a sharp well-defined shadow caused
by calcification.67 Shadowing in dermoids is most frequently
due to attenuation of sound by the mixture of hair and sebum,
rather than due to calcification.73
Another typical feature of dermoids is the Bdermoid
mesh^ appearance that consists of hyperechoic lines and dots
(Fig. 11D).74,75 It is believed to be caused by hair within
nonfatty fluid.1,74,75 This is a useful sign, although fibrin
strands in a hemorrhagic cyst or air in an abscess occasionally
may cause confusion. Fortunately, it seems that, in most
dermoids with this mesh appearance, there is also another
typical finding such as hyperechoic areas, shadowing, or a fatfluid level.
A fluid-fluid level (Fig. 11E) has also been described in
dermoids76,77 but is an infrequent finding.66,71 As an isolated
finding, it may not have much diagnostic value, but there are
often other sonographic features also present that are typical
of a dermoid.66,77 One might expect that the fatty fluid would
be more echogenic and would be the nondependent layer of
fluid. In fact, when there is a fluid-fluid level in a dermoid,
most often, the nondependent fluid is hypoechoic, and the
dependent fluid is hyperechoic.77 Although the nondependent
fluid is always the fatty fluid by CT or MR, the echogenicity
of the fatty fluid by ultrasound is variable.77 Pure sebum,
which is liquid at body temperature, has been reported to be
anechoic or hypoechoic.67 This may be the explanation in
dermoids where the nondependent fluid is less echogenic.
Other lesions such as hemorrhagic cysts, endometriomas, and
ovarian neoplasms will occasionally have fluid-fluid levels,
but in all such cases, the dependent fluid is more echogenic.77
Thus, as an isolated finding, a fluid-fluid level where the
dependent fluid is more echogenic than the nondependent
fluid is not very predictive of any particular pathology.
However, the nondependent fluid will be more echogenic in a
minority of dermoids with a fluid-fluid level (30% in 1
study77). Thus, when the fluid-fluid level has this appearance
with a more echogenic nondependent layer, a dermoid seems
very likely because this pattern was not seen in any other
lesions.77 If one recognizes a floating nodule at the interface
between the 2 fluid layers, this also seems predictive of a
dermoid.77
There is one other appearance that seems very
predictive of a dermoid, but it is uncommon. Different
terminology has been used to describe this appearance, but it
consists of multiple floating globules, spherules, or balls
within a cystic mass (Figs. 11F, 11G).78Y82 Because this is an
uncommon appearance, its predictive value has not been
carefully evaluated, although it has been suggested to be
pathognomonic of a dermoid.78 Such lesions are typically
large cystic masses (usually greater than approximately
10 cm and often 20 to 30 cm), and the globules tend to be
fairly uniform in size. They rarely have any of the other
typical sonographic features of a dermoid as discussed above.
The floating balls are often described as hyperechoic or
markedly echogenic, although, to my review, the echogenicity is not always as hyperechoic as typical of most dermoids.
The globules have been reported to contain hair, sebaceous
debris, keratin, and fibrin.78Y81,83Y87 Occasionally, MR shows
no evidence of macroscopic fat in the floating globules.81
Most ovarian teratomas are benign. Malignant transformation is reported to occur in 1% to 3% of ovarian
teratomas,88Y91 but this is based mostly on pathological series.
Even these low rates seem high in my experience, and I
suspect the frequency is considerably less in clinical practice
because small dermoids are sometimes followed clinically.
Lower malignancy rates of 0.17% to 0.3% for ovarian
teratomas have also been reported.92,93 The malignancy rate
may be higher in postmenopausal women and was reported at
15% in 1 study.94 There is little information in the literature
describing sonographic features that one might use to predict
malignancy of ovarian teratomas. Branching isoechoic solid
components have been suggested as a feature of malignancy.95 The most common histology with malignant
transformation of ovarian teratomas is squamous cell
carcinoma.93 Serum squamous cell carcinoma antigen levels
95
Brown
96
have been suggested as a possible parameter to diagnose
malignancy in ovarian teratomas, but it may be of limited
value.96 With MR imaging, solid components with transmural
extension or contrast enhancement suggest malignancy.97,98
Malignant teratomas are more likely than benign teratomas to
have detectable blood flow within solid areas by color
Doppler ultrasound.96 However, the use of this feature in
clinical practice is not clear because malignant teratomas are
uncommon, and 20% of benign teratomas have some area of
detectable flow by color Doppler ultrasound.96 It was not
clear, however, where the flow was detected in these 20% of
patients with benign teratomas. Another report found that
none of the benign teratomas had detectable flow in the
Bcenter^ of tumor.99 Additionally, struma ovarii, although
also uncommon, may have detectable blood flow. Struma
ovarii, a benign monodermal form of teratoma composed
mostly of thyroid tissue, has a different pathological
appearance from most mature cystic teratomas.100 Its
ultrasound appearance is also variable,100 and struma ovarii
is one of the more difficult lesions to reliably characterize by
ultrasound.101
DOES THE CLINICAL HISTORY HELP?
If the above questions do not lead to a likely diagnosis,
there are a few instances when the clinical history can be
quite useful. This question is mainly to consider the
possibility of TOAs because their sonographic appearance
is quite variable. Generally, one will already be aware of this
possibility based on the clinical presentation before doing the
sonogram. History is also helpful for theca lutein cysts,
although they usually have a characteristic ultrasound
appearance.
Tubo-ovarian Abscess
Tubo-ovarian abscess (TOA) results when a lower
genital tract infection ascends and results in salpingitis and
then ovarian inflammation to the degree that there is
breakdown of normal appearance of the adnexal structures.16
The term tubo-ovarian complex has been suggested when
there are inflammatory changes, but the ovary remains
recognizable by ultrasound.16 The term tubo-ovarian abscess
is suggested when there is further progression of inflammatory change with resulting breakdown of the adnexal
structures such that the ovary is not separately recognized.16
The distinction is important because an abscess may require
drainage, whereas a complex may not.34
Despite ultrasound being a common imaging method in
patients with a suspected TOA, there is surprisingly little in
the literature evaluating ultrasound’s overall usefulness in
this setting.102 There are several studies describing ultrasound
for patients with PID but little actual description of the
sonographic findings for a TOA.16,103Y106 The ultrasound
appearance of TOAs is variable1 (Fig. 12), but they usually
have a cystic component1,106,107 and may have septations,
thick walls, internal echoes, and/or seemingly solid areas. The
appearance overlaps with other lesions including neoplasms34
and hemorrhagic cysts. A minority of TOAs have a tubular
component suggestive of a pyosalpinx.106 The presence of an
associated pyosalpinx, which appears like a hydrosalpinx
but with internal echoes in the fluid is a suggestive sonographic finding.104,106,107 Unless there is a pyosalpinx
component, there does not seem to be a predictive ultrasound appearance for a TOA. Given this variable ultrasound appearance, the clinical findings with signs and
symptoms of PID are helpful,106 if not necessary, to make
the diagnosis of TOA.
Theca Lutein Cysts
Theca lutein cysts typically appear as bilateral cystic
masses with multiple septations.107 They are believed to be
caused by an ovarian response to high levels of human
chorionic gonadotropin. One would likely suspect theca
lutein cysts by their typical appearance (Fig. 13), although
having an appropriate clinical history is helpful in making a
more confident diagnosis. Theca lutein cysts are associated
with gestational trophoblastic disease but can occasionally be
seen with a multiple pregnancy, fetal hydrops, or a normal
FIGURE 11. Mature cystic teratoma. A, Transvaginal ultrasound image of a complex cystic mass reveals that a portion of the
mass consists of a hyperechoic solid component (between the arrows), typical of a mature cystic teratoma (also known as a
dermoid). In this case, there is little, if any, distal shadowing from the hyperechoic component. B, Transvaginal ultrasound
image shows a complex cystic mass (outlined by the calipers) in a different patient. A portion of it consists of a hyperechoic
nodule (arrowheads), from which distal acoustic shadowing (between the arrows) originates. The acoustic shadowing obscures
the deeper portion of the hyperechoic nodule, which has been referred to as the ‘‘tip of the iceberg’’ sign. C, Transvaginal
ultrasound image with color Doppler ultrasound (shown in grayscale) in another patient reveals a uniformly hyperechoic
mass (arrows). Note that there is no flow detected within the mass. Although dermoids are prone to torsion, one should not
expect to detect flow within most dermoids by color Doppler ultrasound. Therefore, when considering ovarian torsion in a
patient with a dermoid, one needs to look for flow in a portion of normal ovary adjacent to the dermoid. D, Transvaginal
ultrasound image in another patient reveals a complex cystic mass with the dermoid mesh appearance, which consists
of hyperechoic lines and dots (some of which are indicated by arrowheads). This mass also contains a hyperechoic solid area
(arrow). E, Transvaginal ultrasound image in a different patient reveals a fluid-fluid level (arrows), with the hyperechoic fluid
being nondependent. F, Transabdominal ultrasound image of another patient demonstrates multiple solid nodules
(asterisks) nondependently within a large cystic mass. This has been referred to as floating fat balls and other names. These
nodules are not as hyperechoic as in some of the more typical dermoids as illustrated above, but the ‘‘floating’’ nature of the
nodules is suggestive of a dermoid. G, Sagittal T2-weighted image with fat saturation of the same patient as in part F
again demonstrates the multiple ‘‘floating’’ nodules. Patient was scanned in the supine position. In this case, there was no fat
evident on T1-weighted sequences with fat saturation. Figure 11F and 11G courtesy of Dr. Peter Hanson and Dr. Karl Stein,
Wabasha, MN.
97
Brown
FIGURE 12. Tubo-ovarian abscess. A, Transvaginal ultrasound
image shows a complex cystic mass (outlined by calipers).
At least 2 locules are seen, each with internal echoes. This
ultrasound appearance may suggest hemorrhagic cysts or
endometriomas, but the clinical setting was suggestive of PID.
B, Transvaginal ultrasound image in another patient shows a
complex cystic mass. This mass contains a mixed cystic and
solid area that may raise concern for a neoplasm. The clinical
setting in this case, however, was suggestive of PID.
appearance of the more common ovarian neoplasms will
usually allow one to favor a particular diagnosis.
Ovarian neoplasms are often grouped into 4 general
histological categories: surface epithelial neoplasms, germ
cell neoplasms, sex cordYstromal neoplasms, and metastatic
neoplasms. Although there are malignant forms in the other
categories, most ovarian cancers are epithelial neoplasms.
Epithelial neoplasms include serous, mucinous, endometrioid, and clear-cell types. Serous and mucinous neoplasms
have benign and malignant forms, whereas endometrioid and
clear cell neoplasms are nearly always malignant. 109
Endometrioid and clear cell carcinomas are the most common
carcinomas to arise in endometriomas.54 Transitional cell
tumors, sometimes referred to as Brenner tumors, are
infrequent epithelial tumors and are usually benign.109
Additionally, borderline tumors have been described for all
surface epithelial cell types but are, by far, most common in
the serous and mucinous cell types.110 Borderline tumors,
sometimes called tumors of low malignant potential or
atypical proliferating tumors, have less stromal invasion than
frankly malignant tumors. Borderline tumors are malignant,
but they carry a better prognosis than frankly malignant
tumors.110 Of the germ cell group of neoplasms, mature cystic
teratomas are by far the most common89 and have been
discussed above. Less frequent neoplasms in this group
include dysgerminoma, yolk sac tumor, and embryonal
carcinoma. These other germ cell tumors are usually solid
but can have areas of cystic change.111 Fibroma is the
most common neoplasm in the sex cordYstromal group;
other neoplasms in this group include thecomas, granulosa
cell tumors, and Sertoli-Leydig cell tumors.112 Metastatic
neoplasms constitute the fourth group and will be further
discussed below.
We will review sonographic features that suggest an
ovarian neoplasm, particularly malignant neoplasms, and then
apply those to the different histological groups of ovarian
neoplasms. The presence of a solid component (Figs. 14AYC),
which is not the typical hyperechoic component of a dermoid,
singleton pregnancy (known as hyperreactio luteinalis).108
This appearance is also the same as seen with ovarian
hyperstimulation syndrome during assisted reproductive
techniques.108 After the high human chorionic gonadotropin
stimulus for their formation is removed, it may take several
weeks for the cysts to resolve.107
IS IT A COMPLEX CYSTIC MASS, OR IS IT A
SOLID MASS?
If the series of questions have not lead to a likely
diagnosis by this point, ovarian neoplasm (other than the
mature cystic teratoma as discussed above) is becoming more
likely. One will not always be able to make a specific
diagnosis at this point, but knowledge of the most frequent
98
FIGURE 13. Theca lutein cysts. Transabdominal ultrasound
image reveals a large cystic ovarian mass (outlined by calipers)
with multiple locules, typical of theca lutein cysts. The other
ovary (not shown) had a similar appearance.
FIGURE 14. Epithelial ovarian neoplasms. A, Transabdominal ultrasound image with color Doppler ultrasound shows a large complex
cystic pelvic mass containing a solid nodular area (between the arrows) that has flow by color Doppler ultrasound. This was a
serous adenocarcinoma of the right ovary. B, Transvaginal ultrasound image in another patient demonstrates a complex cystic mass.
One might consider an endometrioma, in this case, due to the internal echoes; however, there were 2 solid areas that had flow
by color Doppler ultrasoundVone of which is shown in this image (arrow). This was a serous borderline tumor of the right ovary.
C, Transvaginal ultrasound image with color Doppler ultrasound from another patient reveals a complex cystic mass with a
small nodular solid area (arrow) along the wall. Color Doppler ultrasound shows only a small focus of flow at the base of the nodule.
This was a papillary cystadenofibroma of the right ovary. D, Transvaginal ultrasound image in a different patient reveals a
complex cystic adnexal mass with a septation (arrowhead) and solid nodular areas (arrows). This was a borderline serous tumor
of the left ovary. E, Transvaginal ultrasound image from a different patient shows a complex cystic mass (between arrows)
with multiple septations. No solid areas were seen. This was a mucinous cystadenoma. F, Transvaginal ultrasound image shows a
large adnexal mass (between the arrows) that is partly cystic but has a large heterogeneous solid component and a few septations.
This was a clear cell adenocarcinoma. See color plates for images 14A, 14B and 14C on page 93.
is the most useful feature for identifying ovarian malignancy.72,113 Other terminology has been used to refer to these
solid areas, including papillary vegetation, papillary projections, and nodularity. Ovarian cancer is often unilocular and
may not therefore have any septations.72 If septations are
present, thicker septations (typically considered as greater
than 2 to 3 mm) are more typical of malignancy (Fig. 14B).
Ascites, other than the normal trace amount that is frequently
seen in premenopausal women, is also predictive of ovarian
cancer but tends to occur with later stage disease.72 Although
ovarian malignancy is associated with larger masses,5 the
sonographic morphology of a mass is a more useful predictor
of malignancy than its size.72,114 Upon reviewing our data
from a previously published study of 28 ovarian malignan-
cies,72 12 malignant masses (43%) were less than 5 cm in
mean diameter, 8 (29%) were less than 4 cm in mean diameter,
and 6 (21%) were less than 3 cm in mean diameter. In one of
the well-recognized studies of ovarian cancer screening with
sonography, the authors reported volume rather than diameters.115 If one assumes a spherical shape (which I realize is
not likely but would probably skew the calculation to only a
small degree) and calculates the diameter corresponding with
those volumes, 8 (47%) of 17 ovarian malignancies in that
study would have been less than 4 cm in diameter. Although
there is a trend for malignant ovarian masses to be larger than
benign ovarian masses, small ovarian lesions can still be
malignant. Thus, one should not disregard a mass just because
it is small, and should still carefully evaluate its morphology.
99
Brown
For large masses that seem to be simple cysts, careful scrutiny
of all the inner wall is important because tiny solid nodules can
be missed.40
Doppler evaluation initially received lots of interest,
but the pulsed Doppler ultrasound parameters of resistive
index, pulsatility index, peak systolic velocity, and timeaveraged maximum velocity do not allow any significant
improvement over morphological assessment. Thus, the use
of pulsed Doppler analysis is limited.72,116 Optimal characterization occurs with the combination of gray scale
ultrasound for morphological assessment and color Doppler
imaging.117,118 Assessing for solid areas by gray scale
ultrasound and by color or power Doppler imaging to detect
flow within any solid area (Figs. 14A, 14C) are the 2 most
useful features for identifying malignancy.72,116,118Y120
Although one can often predict an ovarian neoplasm by this
combined approach, it may be difficult to distinguish a benign
from malignant neoplasm (Fig. 14D) because benign
neoplasms may also have detectable flow in solid areas.119
The risk of malignancy increases with larger and more
irregular solid components.1 Although probably not widely
done, Doppler ultrasound assessment of vessel size and
orientation may be helpful, with erratic course and changing
caliber of vessels more typical of malignant masses.121
Published studies have evaluated various methods for
categorizing the ultrasound features of ovarian masses,
including gray scale ultrasound alone and in combination
with Doppler imaging. Scoring systems, mathematical models
of probability, and artificial neural networks have been
developed. Although these work fairly well, they are somewhat cumbersome to use. Results of these and other studies,
however, have provided us with the most important features
to assess. Knowing those features and evaluating them in a
subjective method have proven to be useful. Subjective
assessment by an experienced examiner, using proven
sonographic features, is a highly reliable method to differentiate benign from malignant adnexal masses and performs
better than at least some of the mathematical models.122,123
I believe this is the easiest method to incorporate into
most clinical practices, and it has been shown to be reliable.
Thus, it behooves the ultrasound practitioner to be cognizant
of these more reliable ultrasound features.
For complex cystic lesions that are more cystic than
solid, epithelial neoplasm should generally be the first
consideration. Although there are occasional exceptions,
serous and mucinous neoplasms tend to be predominately
cystic with a smaller solid component (Figs. 14AYE).
Endometrioid and clear cell carcinomas (Fig. 14F) tend to
have a larger solid component. Mucinous cystadenomas tend
FIGURE 15. Ovarian fibroma. A, Transvaginal ultrasound
image demonstrates a 7-cm solid mass (between the arrows) in
the right adnexa. It was difficult to know if this was of ovarian
origin because the right ovary was not seen. B, Another
transvaginal ultrasound image from the same patient shows a
tiny echogenic focus (arrow) at the periphery of the solid mass.
Such echogenic foci in the ovaries are not usually thought to be
of clinical significance but, as in this case, can sometimes be
helpful in identifying the ovary.35 C, Transvaginal ultrasound
image in a different patient reveals an area of marked acoustic
shadowing originating within the right adnexa. One might not
recognize the solid mass (labeled M) accounting for the
shadowing and could discount this as bowel gas. However, this
was a consistent well-defined focal area of shadowing during
the scan. Notice that the shadowing does not originate from a
bright interface, as might be expected with shadowing from
calcification, a dermoid, or bowel gas.
100
TABLE 2. Four Questions to Consider When Evaluating
an Adnexal Mass
FIGURE 16. Virilizing stromal neoplasm. A 39-year-old patient
presented with virilizing symptoms and elevated testosterone
levels. Transvaginal ultrasound image demonstrates a subtle,
small, isoechoic mass (labeled M) in the left ovary. Such a mass
could be easily overlooked or attributed to a corpus luteum.
Surgical resection revealed an 11 6 4-mm Leydig cell
tumor of the left ovary.
to appear as cystic masses with multiple septations and no
solid areas (Fig. 14E), whereas serous cystadenomas tend to
be unilocular or bilocular cystic masses with no solid
areas.1,118,124,125 However, the appearance of these benign
lesions overlaps with each other and occasionally with
malignancy, making it difficult to render a confident diagnosis
of serous or mucinous cystadenomas in some cases.1
When a tumor is predominately solid, one should
consider the sex cordYstromal group of tumors. Although
some of the tumors in this group, particularly if larger, can
have a cystic component; many are solid. The most common
FIGURE 17. Metastasis to the ovary. Transvaginal ultrasound
image reveals a solid mass (labeled M) replacing the left ovary.
The right ovary (not shown) appeared similar. This was caused
by metastasis from breast cancer.
1. Is the adnexal mass extraovarian in origin?
If so, consider more common lesions such as
paraovarian cyst
hydrosalpinx
Peritoneal inclusion cyst
2. If the mass is ovarian in origin, is it one of the BBig 5^?
Evaluate for suggestive features of a
simple cyst
hemorrhagic cyst
corpus luteum
endometrioma
mature cystic teratoma (dermoid)
3. Does the clinical history help?
Mainly to consider tubo-ovarian abscess or theca lutein cyst
4. Is it a complex cystic mass or is it a solid mass?
Evaluate for solid areas not typical of a dermoid and use color or power
Doppler ultrasound to assess for flow in the solid areas. These
findings are useful for predicting neoplasms.
If more cystic than solid, consider epithelial neoplasms first.
If mostly or entirely solid, consider sex cordYstromal neoplasms first if
unilateral and metastases if bilateral.
neoplasm in this group is the fibroma. It usually appears as a
solid mass that can be homogeneous or heterogeneous and
may attenuate sound (Fig. 15).126Y130 Occasionally, it can
have marked attenuation of sound (Fig. 15C).126,128,130
Fibromas are almost always benign tumors. There is a
spectrum with thecomas, and both histological types can
occur in the same tumor. The thecoma component can secrete
estrogens. Fibromas have a similar appearance to uterine
leiomyomas. Thus, when one identifies a solid adnexal mass
but does not identify an ipsilateral ovary, the primary
differential diagnosis is ovarian fibroma versus pedunculated
leiomyoma. Granulosa cell tumors are low-grade malignancies and are the most common ovarian tumor to secrete
estrogen.127 In my experience and that of others,127 granulosa
cell tumors are commonly solid, although a complex cystic
appearance with solid areas or septations has been
described.131 Estrogen secretion from granulosa cell tumors
can cause endometrial thickening and abnormal vaginal
bleeding.131 Sertoli-Leydig cell, and other related, tumors are
also part of the sex cordYstromal group. It is the most
common ovarian tumor to secrete androgens and can cause
virilizing symptoms.127,132 Most virilizing ovarian neoplasms
are small solid tumors that can be subtle (Fig. 16).127,132
When a virilizing ovarian neoplasm is being considered, one
should be suspicious of any subtle abnormality in the ovary
and at least obtain a follow-up ultrasound. Occasionally,
these tumors can have a cystic component.127 When faced
with a seemingly solid lesion, one should also consider
mimics of solid ovarian masses: pedunculated uterine
leiomyoma, chronic endometrioma, and subacute hemorrhagic cyst. Brenner tumor is an uncommon benign epithelial
tumor that also tends to be solid and may coexist with other
ovarian neoplasms.133,134
101
Brown
Metastatic neoplasms have a variable appearance.
When considering all types of ovarian neoplasms, there
are few features useful in distinguishing primary versus
secondary ovarian malignancy.135 Multilocularity is more
common, however, in primary, versus secondary, neoplasms.135 The most common primary sources of metastasis
to the ovary include breast, colon, gastric, and appendiceal
carcinomas.136Y140 When considering these more frequent
primary sources, the presence of bilateral solid masses
(Fig. 17) is suggestive of metastases.34,141Y143 Metastasis to
the ovaries from breast cancer usually occurs in the setting
of advanced stage disease.144,145 It is more variable whether
metastasis from other primary tumors have a known
primary carcinoma before the metastasis is discovered.135
19.
SUMMARY
20.
Knowing the most useful sonographic features for
common benign tumors, which are different from the
sonographic features of most malignant tumors, will allow
one to make a confident diagnosis or generate a short list of
differential diagnoses in most cases. Progressing through
these series of 4 questions is 1 approach to the sonographic
diagnosis of adnexal masses that I have found to work well.
Table 2 briefly summarizes this approach. There will be
occasional problematic cases, whether because of limited
scan quality, confusing sonographic appearance, or rare
lesions that are not easily characterized, but this approach
works well for most adnexal masses.
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A Practical Approach to the Ultrasound Characterization of Adnexal

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