“Making a Sound Diagnosis”. - International Skeletal Society

“Making a Sound Diagnosis”.
Sonography of Soft Tissue
Masses: Technique, Pearls and
Pitfalls to Keep Radiologists
out of Danger
Bradley J. Carra, MD
Liem T. Bui-Mansfield, MD
Dillon Chen, MD
Seth D. O’Brien, MD
Department of Radiology
Brooke Army Medical
Center, SAMMC
San Antonio, TX 78234
Category of paper: Educational review EE05
Corresponding author:
[email protected]
Disclosures
1. The authors do not have a financial relationship
with a commercial organization that may have a
direct or indirect interest in the content.
2. The opinions expressed on this document are
solely those of the author(s) and do not
represent an endorsement by or the views of the
United States Air Force, the Department of
Defense, or the United States Government
Goals/Objectives
• Describe role of US in work-up of soft tissue masses
of the extremities
• Review normal appearance of superficial soft tissues
on ultrasound
• Emphasize importance of proper technique for
evaluating masses with ultrasound
• Review masses with characteristic appearance on
ultrasound
• Illustrate potential pitfalls of evaluating soft tissue
masses with ultrasound
• Target audience: radiologists, orthopedists, primary
care physicians
Outline
• Introduction
• Role of ultrasound (US) in work-up of soft
tissue masses
• Technique
• US appearance of normal soft tissue
• Masses with characteristic ultrasound
appearance
• Potential pitfalls
• Conclusion
Introduction
• Ultrasound has traditionally had a limited role in
evaluating soft tissue masses
• More cases of palpable soft tissue masses are being
referred to US for initial (before x-ray, CT, or MRI)
evaluation due to its availability, portability, and low
cost
• It is important for general radiologists to know
strengths and limitations of ultrasound when
evaluating soft tissue masses
Role of Ultrasound in Work-up
of Soft Tissue Masses
• Confirm presence of mass
• Characterize mass
–
–
–
Solid versus cystic
Vascularity
Dynamic information (e.g., compressibility)
• Diagnose mass if possible
• Guide percutaneous intervention
Strengths of Different Modalities
US
1.
2.
3.
4.
Radiography
or CT
Determine solid
1.
versus cystic
Determine
2.
vascularity
Dynamic
information (e.g.,
compressibility)
Direct interaction
between patient and
radiologist
Determine osseous
involvement
Determine pattern
of calcification
MRI
1.
2.
High contrast
resolution
Clues to tissue
composition
Technique: Ultrasound Evaluation of Soft
Tissue Masses
Superficial Masses
Deep Masses
Transducer
Linear, high frequency (12,
15, 17 MHz)
✍Higher spatial resolution
✍Decreased penetrability
Curved array, low
frequency (5, 9 MHz)
-Decreased spatial
resolution
-Increased penetrability
Gel Cushion or
Stand-off pad
Yes
-Stand-off pad more rigid
-Gel allows for acquisition
of more dynamic
information
No
Pressure
Light pressure
-Avoid compressing small
vessels and missing flow
Deeper pressure may be
necessary
Image Acquisition
Static images
Panoramic view
• Allow for detailed
Multiple static images compiled into
characterization of mass:
single image
●
–
–
–
–
–
Echogenicity
●
Better evaluate size, extent, and
Internal architecture
relationship to surrounding
Evaluation of borders
structures
Increased through
Cine loop
transmission
●
Better evaluate extent and origin of
Assessment of vascularity
lesion
with color Doppler and
●
pulsed-wave or duplex
Dynamic information
(compressibility, pulsatility, shifting
structures indicating fluid)
Cine loop
Dynamic images demonstrating compressibility of ganglion cyst
Normal Structures on Ultrasound
Structures
Epidermis/Dermis
Hypodermis
Tendon
Muscle
Bone and Calcium
Sonographic Appearance
Hyperechoic
Hypoechoic fat and hyperechoic fibrous septa
Hyperechoic with fiber-like echotexture
Hypoechoic
Hyperechoic with posterior acoustic
shadowing
Hyaline cartilage Hypoechoic and uniform
Fibrocartilage
Hyperechoic
Ligaments
Hyperechoic, striated; more compact than
tendon
Peripheral nerves Fascicular; nerve fascicles hypoechoic with
surrounding hypoechoic connective tissue
Lymph node
Hypoechoic oval mass with central
echogenicity
Typical appearance of superficial structures on ultrasound
US Gel
Fat
Muscle
Fascia
Epidermis/Dermis
Wrist
Tendon
Bone Cortex
Lymph Nodes
Fatty Hilum with Flow
Knee
Soft Tissue Masses on US
• Majority of soft tissue masses have
nonspecific appearance on ultrasound
• Some features allow radiologists to
confidently make certain diagnoses:
–
–
–
–
LOCATION of mass
Relationship to surrounding structures
Vascularity of mass
Dynamic information
Location of Abnormality
• Ultrasound has limited contrast resolution, but excellent
spatial resolution1
–
–
Axial resolution 10 MHz probe = 150 µm
MR resolution 1.5T, 12 x 6 cm FOV, 256 x 256 matrix, slice
thickness 0.5 cm = 469 µm
• Soft tissue masses on ultrasound have characteristic
appearance based on LOCATION
–
–
–
Extremity
Anatomic compartment
Relationship with surrounding structures, joints
• US is well suited to evaluate location due to its excellent
spatial resolution
1Nazarian, L. AJR 2008;190:1621-26
Example #1: Hip mass after a
fall. Diagnosis?
A. Hematoma
B. Morel-Lavallee
lesion
C. Abscess
D. Sarcoma
E. Trochanteric bursitis
Morel-Lavallee Lesion
• Pathology:
–
–
Post-traumatic closed degloving injury between
fat and muscle fascia
Creates potential space filled with blood, lymph,
fat
• Ultrasound appearance:
–
–
–
–
Hypoechoic, anechoic fluid collection
Compressible
Lack of internal flow
May contain globules of echogenic fat
Morel-Lavallee Lesion
• LOCATION:
–
–
Classically over greater trochanter of hip
Between subcutaneous fat and muscle fascia
• Differential diagnosis:
–
–
Acute: hematoma, abscess, fat necrosis, neoplasm
Chronic: neoplasm, seroma, lymphocele
• Diagnosis suggested based on characteristic
location with appropriate history
Example #2: Diagnosis of this
supraclavicular mass?
A. Soft tissue sarcoma
B. Lymphoma
C. Metastasis
D. Acromioclavicular
joint cyst
Nonspecific cystic mass.
Diagnosis is made by
recognizing origin from
acromioclavicular joint
Acromioclavicular Joint Cyst
• Pathology:
–
–
Chronic full thickness tear of rotator cuff results in high riding humeral
head causing friction and resulting in tear of inferior AC joint capsule
Established communication between glenohumeral and AC joints allows
effusion and bursal tissue to enter AC joint, distending the superior AC
joint capsule and forming a cystic mass
• Ultrasound appearance:
–
–
Anechoic, hypoechoic
Lack of internal flow (exception: synovitis)
• LOCATION:
–
–
Superior to AC joint
Demonstrates communication with AC joint, so called “Geyser sign”
Pearls
• Certain diagnostic cystic masses detected on
ultrasound may need additional MRI
–
–
Acromioclavicular joint cyst
Parameniscal cyst or paralabral cyst
• Purpose:
–
Confirm underlying pathology
●
●
–
Exclude complication
●
–
Rotator cuff tear
Meniscal tear or labral tear
Suprascapular neuropathy
Guide management
Soft Tissue Masses with Characteristic Location Allowing
Potential Diagnosis on US
Location
Cystic
Solid
Shoulder
AC Joint cyst
Paralabral cyst
SASD bursitis
Elastofibroma
Elbow
Olecranon bursitis
Tumoral calcinosis
PNST
Epitrochlear lymph node
Wrist/hand
Ganglion cyst
PNST
GCTTS
Glomus tumor
Palmar fibromatosis
Hip/thigh
Morel-Lavellee
Trochanteric/iliopsoas/ischial
bursitis
Intramuscular myxoma
Inguinal/femoral hernia
Knee
Baker cyst
Parameniscal cyst
Joint effusion/synovitis
Ankle/foot
Ganglion cyst
Morton’s neuroma
PNST
Plantar fibromatosis
Acromioclavicular (AC); Subacromial subdeltoid (SASD); Peripheral nerve sheath tumor (PNST); Giant cell tumor of the tendon sheath (GCTTS)
Case #1: Which of these is a
lipoma?
A. A
B. B
C. C
D. None
Lipoma
Potential Pitfalls
A
Epidermal
Inclusion Cyst
B
Liposarcoma
C
Pitfall #1: Sonography cannot
accurately diagnose lipoma
• Lipoma is the most common soft tissue
neoplasm
• Pathology
–
–
Benign proliferation of fat cells with various
amounts of fibrous tissue
May arise within subcutaneous fat, muscle, or
even bone
• Ultrasound appearance:
–
Classic: well-defined, smoothly marginated,
hypo- to iso-echoic, pliable, little to no internal
flow
Sonography of Lipoma
• Variable, nonspecific appearance is most
common
–
–
Echogenicity depends on amount of water, fat,
and fibrous tissue, which is variable
Relative echogenicity depends on surrounding
tissue
• Accuracy of sonographic diagnosis
–
Ranges from 49-64%2
2Inampudi, P., et al. Radiology. 2004;233:763-767
Pearls
• Any concerning findings should prompt additional imaging
evaluation
–
Concerning ultrasound findings:
●
Large size, marked internal vascularity
–
Concerning clinical findings:
–
Growing mass, pain
MRI can confirm fatty nature of mass, determine soft tissue component
●
• Additional evaluation
–
–
Image guided percutaneous biopsy can be attempted, but sampling error
must be kept in mind
Excisional biopsy only method for definitive diagnosis
• In absence of concerning findings, surveillance ultrasound may
be reasonable
Case #2: Thigh mass after
trauma. Diagnosis?
A. MorelLavellee lesion
B. Soft Tissue
Neoplasm
C. Epidermal
Inclusion Cyst
D. Hematoma
Internal vascularity favors
solid mass over hematoma
Pitfall #2: Sonography cannot reliably
distinguish hematoma from solid soft
tissue neoplasm
• Soft tissue sarcomas are far less common
than hematomas in the extremity
• Risk factors for development of hematoma:
–
–
–
Direct trauma
Bleeding diathesis
Anticoagulation therapy
Sarcoma versus Hematoma
• Disorganized vasculature of sarcoma can result
in hemorrhage, making distinction difficult3
• Sarcomas mimicking hematomas3
–
–
–
–
–
Angiosarcoma
Synovial sarcoma
Extraskeletal Ewing sarcoma
Liposarcoma
Malignant fibrous histiocytoma
• MRI more useful than CT in demonstrating
enhancement of sarcomatous component
3Imaizumi S, Morita T, Ogose A et al. J Orthop Sci 2002;7:33-7
Distinguishing Features of
Hematoma and Sarcoma
Hematoma
Sarcoma
History
Trauma, coagulopathy,
surgery
NO risk factors
Location
Unicompartmental,
adjacent to myotendinous
junction
Multicompartmental
US Appearance
Initially hypoechoic
Mixed echogenicity over
time
NO internal vascularity
Variable echogenicity
+/- internal vascularity
MR Appearance
Follow specific stages of
hemorrhage
Perilesional edema
Thin peripheral
enhancement  low T2
Different stages of
hemorrhage
Heterogeneous central
nodular enhancement
Evolution of lesion
Decrease in size
Increase in size
Pearls
• Corroborate history of trauma or bleeding disorder
• Carefully scrutinize mass for vascularity
• Obtain MRI in ALL suspicious cases
• Avoid aspiration biopsy until complete imaging evaluation
has been performed (and beware of sampling error)
• Follow-up ultrasound to demonstrate retraction may be
reasonable in low-risk cases with history of significant
trauma or bleeding disorder
Case #3: Primary soft tissue mass or underlying bone
lesion. Which of these is a primary soft tissue mass?
A
B
A. A
B. B
C. A & B
D. Neither
Osteochondroma of humerus
Soft tissue abscess and
osteomyelitis with sequestrum
Pitfall #3: Sonography may not be able
to determine if a palpable mass is truly
of soft tissue origin or extraosseous
manifestation of underlying osseous
pathology
• Ultrasound poorly evaluates osseous structures
and marrow
• Calcified soft tissue masses, which may be
extraosseous extensions of osseous pathology,
cause posterior acoustic shadowing, limiting
evaluation of deep aspect of the mass
Pearls
• Cine loops or panoramic images may
help determine origin of mass and its
relationship to adjacent structures
• If entire mass cannot be demonstrated,
proceed to CT or MRI!
Conclusions
• US is being increasingly utilized as initial imaging
modality for evaluation of soft tissue masses
• Technique is important for demonstrating full extent of
mass, relationship to surrounding structures, and to
accurately characterize the mass
• Role of US in evaluating soft tissue masses:
– Confirm presence of mass
– Determine solid versus cystic
– Assess vascularity (indicating solid mass or cystic
mass of vascular origin)
– Diagnose mass, if possible
Conclusions (continued)
• High spatial resolution of US allows for
accurate determination of anatomic location of
mass and relationship to surrounding structures
• Confident diagnosis of select masses can be
made based on certain imaging findings in
characteristic LOCATIONS
• Otherwise, US findings are mostly nonspecific and further evaluation is warranted
Conclusions (continued)
• There are many potential pitfalls of which
radiologists must be aware
–
–
–
–
–
Inaccuracy in diagnosing lipoma
Distinguishing hematoma from sarcoma
Extra-osseous manifestations of osseous pathology
Distinguishing infected from non-infected fluid
collection*
Pseudocystic appearance of solid masses*
• Avoiding pitfalls will result in more accurate
diagnosis and prevent delay in diagnosis and
treatment of potentially malignant masses
* Not discussed in presentation