Symptomatic adrenal myelolipoma: therapeutic considerations
European Journal of Surgical Oncology 1995; 21:403-407
Symptomatic adrenal myelolipoma: therapeutic considerations
C. Spinelli, G. Materazzi, P. Berti, M. Cecchi, G. Morelli and P. Miccoli
Dipartimento di Chirurgia, Universit~ di Pisa, Via Roma 67, 56100 Pisa, Italia
Four cases of symptomatic myelolipoma of the adrenal gland are presented. Three were treated at laparotomy and one
with a laparoseopic approach. On the basis of these four cases we discuss the aetiology, pathogenesis, clinical manifestations,
diagnosis and treatment of this rare disease. We also report the follow-up of a patient with bilateral myelolipoma, who
underwent monolateral excision.
We conclude that myelolipoma, if correctly diagnosed, can be treated conservatively with careful follow-up, limiting
surgery to symptomatic cases.
Key words: myelolipoma; adrenal gland; adrenal masses.
Myelolipoma is a rare benign non-functioning tumour of
the adrenal gland. It is characterized histologically by the
presence of mature adipose tissue containing foci of haematopoietic bone marrow cells.~ Before the introduction of CT
and US these tumours were rarely diagnosed during life. In
1977, 190 cases were reported, 2 most of which had been
found incidentally during autopsy. Myelolipoma only
becomes symptomatic when large. In our department from
1988 to 1994, 28 incidental adrenal masses were surgically
removed. Four cases were symptomatic adrenal myelolipomas. In this study we report details of the findings,
diagnosis and surgical strategy of the four cases, one of
which one was bilateral.
LF, a 43-year-old woman, had intermittent pain for 8
months in the left upper quadrant radiating to the flank.
Her clinical history was not significant and physical examination was negative.
Laboratory studies and results of urinalysis were normal.
Serum electrolytes and urea were within normal values.
Plasma coi'tisol, urinary alpha-ketosteroids, cathecholamines and urinary VMA were also within normal ranges.
An abdominal ultrasound scan revealed a 10-era diameter
highly echogenic mass in the left adrenal region.
CT revealed a soft tissue mass in the region of the left
Surgery was performed through a transverse left abdominal incision. The left adrenal mass was exposed after incision
of the colo-epiploic ligament and mobilization of the
stomach, spleen and pancreatic tail.
The mass measured 11 cm in diameter, was spherical and
weighed 90 g. T h e surface was smooth and yellowish. The
0748-7983/95/040403+ 05 $08.00/0
cut surface revealed a yellow solid tumour with sporadic
haemorragic areas. Histologically the tumour consisted
almost entirely of fat with foci of typical [;one marrow
elements consisting of precursors of the erythroid and granulocytic series.
The patient was discharged 7 days after surgery.
The patient shows no sign of disease 6 years postoperatively.
FA, a 48-year-old man, complained of lumbar tenderness
and abdominal discomfort for 5 months. Physical examination of the abdomen was negative. The laboratory and
endocrine studies were normal. Ultrasound scan revealed
two hyperechogenic masses, of about 5 cm and 2 cm in
diameter, respectively, in the right and in the left adrenal
Abdominal CT revealed two circumscribed inhomogeneous fat masses, with low density, in the same area.
Exploration was performed with a tranverse upper
abdominal incision; only the mass on the right was removed
because its dimensions were larger. The tumour was easily
dissected from surrounding structures and blood loss was
minimal. The total weight ofthe mass was 38 g. Pathological
diagnosis was adrenal myelolipoma. Convalescence was normal, and the patient was disharged a week postoperatively.
The patient was seen regularly for follow-up and 5 years
after treatment is healthy and free of symptoms. The left
myelolipoma which had not been surgically treated has not
undergone volume alterations on ultrasound and tomographic evaluation.
DP, a 57-year-old-man, was admitted to hospital with a
complaint of intermittent lumbar and subscapular pain
C. Spinelli et al.
Fig. l. Abdomen US: adrenal myelolipoma (Case 4): hyperechogenic mass ( I0 cm) on the upper pole of the right kidney.
which increased with respiration. Physical examination and
laboratory assays of blood and urine did not disclose any
abnormality. Determination of adrenal hormones was
normal. US revealed a capsulated tumour of 6 cm in diameter. CT scan showed a 4.5 x 5.5 cm mass with regular edge,
extremely low in density and with an irregular 1.5 cm area
within. A transverse upper abdominal incision was performed and a large (7 x 5 × 3.5 cm) mass was excised in its
entirety with the adrenal gland. The weight of the mass was
100 grams. Histological examination confirmed the diagnosis of adrenal myelolipoma with aspects of nodular hyperplasia of the cortex and irregular areas of calcification. The
patient's post-operative recovery was uneventful and he is
healthy and free of symptoms one year after surgery.
TR, a 44-year-old man, was referred with lower abdominal
pain radiating to the lumbar region of about 1 year's
duration. Physical examination, blood samples and urine
assays of adrenal hormones were normal. The ultrasound
showed a 10-cm hyperechogenic mass on the upper pole of
the right kidney (Fig. 1). CT revealed a mass between the
liver and the right kidney that was heterogeneous in density
and with little contrast enhancement for the presence of fatty
tissue (Fig. 2). The tumour was removed using a
laparoscopic approach. This patient represented the 27th
case of laparoscopic adrenalectomy in our experience. 3
The patient and the trocars were placed as Gagner
suggested. 4 The operating table was in the anti-trendelenburg position and inclined at 4Y. Five trocars were
positioned as follows: the first 10 mm trocar at the lower
edge of the umbilicus to insert the laparoscope; The second
10 mm trocar in the subcostal position on the right mid-
clavicular line in order to use the retractor with five digits.
A third 10-ram trocar was positioned at the intersection of
the umbilical line and the median right axillary line to insert
the Kelly clamp and Babcock forceps. A fourth 10-mm trocar was placed at the same site to insert electrified scissors
and a 5-mm trocar at the intersection of the right anterior
axillary line and the last rib to insert the aspiratory and
washing tube. By cutting the right triangular ligament and
opening the posterior peritoneum we accessed the right adrenal region. Intraoperative ultrasound facilitated the investigation of the adrenal vascular pedicle and the relationships
to the inferior cava.
Using a sterile plastic bag we extracted the mass whole
thus avoiding fragmentation in the peritoneal cavity. The
mass measured 10 × 9 x 4 cm and weighed 85 g. The histological diagnosis was myelolipoma (Figs 3, 4). The patient
was discharged 3 days post-operatively after a satisfactory
Adrenal myelolipoma affects both males and females, with
a higher occurrence around the fifth and sixth decades of
life, although in the literature there are cases in the pediatric
and geriatric ages. 5 In most cases, myelolipoma is monolateral, rarely, bilateral. In a review of 59 well-documentated
cases of surgically removed adrenal myelolipoma only one
patient had bilateral tumours/'
The size of these tumours vary from a diameter of only a
few mm to more than 15 cm. On average, when diagnosed,
their diameter is 5 cm, although tumours of 34 cm and
weighing 5500 gr 7 have been reported. This neoplasia exists
in 0.08~).2% of autopsy reports 7'8 and it represents about
8% of adrenal incidentalomas.9"~°They are usually asympto-
Fig. 2. Abdomen CT: voluminous, heterogeneous mass of tile right adrenal gland (7.5 × 9, 5 × 7.5 cm) with little contrast enhancement for
the presence of fatty tissue (Case 4).
Fig. 3. Section from adrenal myelolipoma ( x 65) (Case 4): mature
fat and haematopoietic tissue displacing adrenal cortical cells.
Fig. 4. Section from adrenal myelolipoma (× 65) (Case 4): haematopietic tissue containing cells at different stage of maturation.
matic and have no endocrine activity. Non-specific abdominal pain is the most common symptom, secondary to
mechanical compression from large tumour bulk, hemorrage
or intratumoral necrosis. ~ There are also reports of myelolipomas presenting with unusual epigastric pain. ~-' Rare
symptoms can include haematuria and hypertensionYT M In
the literature a large number of cases of an association
between myelolipoma and endocrine diseases have been
reported such as pathological obesity, hermaphroditism,
Addison's disease, Nelson's syndrome, Cushing's disease
and Conn's syndrome, t'~5"~6
Endocrine investigations in order to differentiate functioning from non-functioning tumours of the adrenal gland
include serum cortisol, serum cathecolamines, 24-hour urinary VMA, metanephrines, free cortisol, 17-hydroxysteroids, 17-ketosteroids and plasma aldosterone levels.
The aetiopathogenesis of this disease is unknown, although
a large number of theories have been put forward: ectopia
of myeloid tissue, embolism of bone marrow elements,
hamartosis, metaplasia, degeneration of cortical cells,
haematopoietic proliferation of substances formed by
Grossly, myelolipoma is a yellowish, roundish, well-circumscribed mass, even if it does not have a true capsule.
Microscopically, myelolipomas consist of mature adipose
tissue with scattered islands of haematopoietic cells, more
frequently belonging to the granulocyte series, but also to
the astrocytes; lymphocytes and megalokaryocytes are rare.
Patients with myelolipoma do not have haematopoietic diseases and have normal bone marrow.
Before ultrasound and CT, myelolipomas could be identified only when a standard abdominal X-ray showed a suprarenal, transparent mass. Now the imaging allows more and
C. Spinelli et al.
more frequent diagnosis of these unusual adrenal tumours.
The sonographic and tomographic appearance of myelolipoma depends on the structural characteristics of the
tissues that it is composed of. These lesions can contain
adipose and myeloid tissue in different proportions. The
tumours with a higher adipose content are more correctly
identified with US and CT. On the contrary, myelolipoma
containing less fat and more myeloid tissue, hemorragic
areas and sporadic calcifications are more difficult to differentiate from other adrenal neoplasms. ~7't8More often these
lesions are solid masses with well-defined edges. They are
hyperechogenic on US and low in density on CT; very rarely
the masses are composed of myeloid tissue which would
show up as hypoechogenic on US and have CT densities
well within the range of fat before contrast enhancement.~9'2°
Images after contrast enhancement give only an improvement in detecting the edges of the lesion in respect to the
adjacent organs, the liver and the kidney, but they do not
provide any other information?° In spite of the sensitivity
of US in showing adrenal masses greater than 2 cm, -'~ echopattern of myelolipoma is not pathognomonic, thus it is
necessary to verify them with CT or MRI. CT is the most
precise procedure for detecting adrenal myelolipomas. MRI
sagittal and coronary sections are more precise than CT to
detect these tumours.-'" M RI can distinguish between adrenal
haemorrhages, adenomas, metastases and pheochromocytomas) 2'23 On MRI, myelolipomas usually have an increased intensity relative to the liver on both short and long
TR/RE sequences depending on the amount of fat) 9
They may be inhomogeneous or low in intensity, depending
on the percentage of other tissue components present in the
tumour, t5'24The differential diagnosis of a suprarenal fatty
mass includes myelolipoma, renal angiomyolipoma expanding from the upper pole and retroperitoneal lipoma, which
are entirely fat-containing masses, whereby myelolipomas
are a mixture of fat and other tissue. Liposarcomas of the
adrenal gland or retroperitoneum are large lesions and
should not be confused with smaller and well-defined myelolipomas, t7
Angiomyolipoma are very vascular tumours and can be
diagnosed using angiography.-'L2SThe differential diagnosis
between liposarcoma and myelolipoma is often impossible.~t
Green-'6reported a case of adenocarcinoma metastatic to the
adrenal gland simulating myelolipoma. The lesion infiltrated
a portion of the retroperitoneum adipose tissue creating a
false image of intralesional fat. Cytological examination
with fine-needle aspiration under tomographic control can
be useful for dianosis in difficult casesY Myelolipoma usually tends to grow very slowly. In the literature only four
cases of long-term follow-up have been reported. In the case
described by Liebman ~t and in the one by Del Gaudio -'8 the
masses had increased modestly after observation for 5 years
and 13 years, respectively. Wilhelmus29reported a case which
was observed over 52 years, from the age of 18 to 70 years
in which the mass had reached large dimensions (30 x 22 x 16
cm) and a weight of 5500 grams. Also in the clinical case
reported by Meaglia 5 after 4 years of accurate examination,
an increase in volume was observed associated with symptomatology such as to make surgical ablation necessary. In
our case no significant increase in volume has been observed
after an accurate follow-up of 4 years. Therefore myel-
olipomas, if asymptomatic and less than 4 cm, can be
entrusted to accurate follow-up3° avoiding traditional surgical ablation. Currently laparoscopic surgery is being used
more fre.quently than traditional surgery.4'3~'3"- The anatomical position and the dimensions of the masses do not
pose an absolute limit to the use of laparoscopy, according
to the most recent experiences. 33 The advantages of laparoscopic surgery include a faster and better postoperative
recovery. The increase in laparoscopic surgery will reduce
the number of patients who are subjected to a long followup because of non-functioningadrenal masses.
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Accepted.for publication 11 April 1995