Myelolipoma of the Adrenal Gland

Timothy J. Pagana, MD, Philadelphia, Pennsylvania

Steven J. Karasick, MD, Philadelphia, Pennsylvania

David Karasick, MD, Philadelphia, Pennsylvania Leroy H. Stahlgren, dD, Philadelphia, Pennsylvania

Myelolipoma is a nonfunctioning benign tumor of the adrenal gland which consists of hematopoietic and adipose tissue [I]. The tumor was first described by Gierke [2] in 1905, and named by Oberling [3] in 1929. Most series consist of myelolipomas discovered incidentally at autopsy. We report the 14th patient whose tumor was clinically recognized and removed successfully.

Case Report

Our patient was a 65 year old woman whose chief com- plaint was intermittent back pain and malaise. She had a long history of hypertension. Findings on physical exami- nation were normal except for obesity and hypertension. Blood pressure was 180/100 mm Hg. All routine blood studies were normal. Microscopic hematuria was noted. Endocrine studies including renin, catecholamine, vanil- lylmandelic acid, hydrocortisone and ketosteroid deter- minations gave normal results.

Findings on roentgenography of the abdomen were normal. Intravenous pyelography revealed lateral and anterior displacement of the upper pole of the right kidney (Figure 1). Ultrasound confirmed that finding and revealed an area in which echoes were increased posterior to the kidney (Figure 2). Computed tomography showed that the tumor was above and posterior to the kidney and consisted of tissue with a density consistent with fibrosarcoma (Figure 3). Arteriography demonstrated that the mass was avascular.

Operation was carried out through a transverse ab- dominal incision extending to the right flank. A well-cir- cumscribed mass arising from the adrenal gland was identified and excised along with a segment of the gland.

The tumor was 8 by 6 cm, egg-shaped, yellowish tan and encapsulated by normal-appearing adrenal cortical tissue (Figure 4). The cut surface was predominantly fatty and contained well-delineated nodules. Microscopy revealed

From the Department of Surgery, Episcopal Hospital, Philadelphia, Penn- sylvania.

Requests for reprints should be addressed to Timothy J. Pagana, MD, Department of Surgical Oncology, Roswell Park Memorial Institute, Buffalo, New York 14263.

282

myeloid and erythroid cells, megakaryocytes and normal adipose tissue (Figure 5). There was an encapsulating rim of attenuated adrenocortical tissue (Figure 6). Selected sections revealed hemorrhage.

The patient’s postoperative recovery was uneventful.

Comments

Pathology: The reported incidence of this tumor in autopsy series varies from 0.08 to 0.8 percent [4,5]. The tumor originates in the adrenal cortex. Its sur- face consists of a pseudo-capsule of compressed zona glomerulosa and fasciculata. The size varies, although tumors which are recognized clinically may be quite large.

Myelolipoma consists of variable amounts of lipoid and hematopoietic cells (myeloid or erythroid, or both) [6]. Fat necrosis and hemorrhage were com- monly seen in the tumors that were symptomatic. In some cases, calcification occurred in those areas.

Sob [7] has defined two types of myelolipoma. Type I, which includes our case, is yellowish orange and predominantly lipomatous, associated with minimal hematopoietic elements, which are mostly erythroid. Type II is reddish brown, and myeloid elements predominate. In previous reports [8,9] little importance was given to So& classification. In fact, Karstaedt [IO] suggests that a diagnosis of myeloli- poma can be made reliably with ultrasound and computed tomography alone, thereby obviating the need for exploratory surgery. In light of So&s’s au- topsy finding that myelolipomas may vary in density, differentiation from other possible tumor tissues using ultrasound and computed tomography is un- certain.

Etiology: Theories about the cause of this tumor include choristomal embryonal fault, extramedullary hematopoiesis, embolism of bone marrow cells and cortical cell metaplasia [II]. The most commonly held theory suggests that undifferentiated mesen- chymal cells within the adrenal cortex are stimulated

erlcan Journal of Surgery

Myelolipoma of the Adrenal Gland

Figure 1. intravenous pyeiogram showing lateral displacement of the upper pole of the right kidney.

Figure 3. Computed tomographic scan delineating the tumor (marker) posterior to the right kidney.

to differentiate into the myeloid and lipoid lines [12,13]. The nature of this stimulus is unknown.

Clinical picture: Myelolipomas, like other retroperitoneal tumors, may cause symptoms due to bleeding or displacement of adjacent organs. Pain is the most consistent symptom and is usually caused by hemorrhage within the tumor (Table I). Hema- turia was noted in 5 of the 14 patients. The cause is unclear. Although not mentioned in earlier reports, obesity and hypertension occur more frequently than in the normal population (Table I). None of the clinically recognized tumors have been associated with endocrine dysfunction. The age of the patients varied from 41 to 67 years, and the incidence was equal in men and women.

Plaut [I], whose series was based on autopsy findings, reported a higher incidence of severe chronic debilitating disorders such as carcinomatosis

Figure 2. Transverse sonogram showing an echogenic mass (arrows) posterior to the right kidney.

Figure 4. Resected specimen containing normal adrenal tissue (solid arrow) and myeioiipoma. Note the combination of iipo- matous tissue (asterisks) and nodules of solid cellular tissue (open arrow).

Figure 5. Photomicrograph showing iipomatous tissue (arrow) in a myeioid cellular stroma. Ail bone marrow elements are present. (Magnification X3.5, reduced 50 percent. )

Volume 141, February 1981 283

Pagana et al

Ffgure 6. The tumor surrounded by a “pseudocapsule” (arrow) of attenuated adrenal cortex. (Magnification X3.5, reduced 43 percent. )

TABLE I Data on the 14 Reported Cases

and suggested a relation between myelolipomas and chronic illness. Our review of the reported cases does not support that thesis.

Role of special studies: The most useful screen- ing tests are conventional urography and high dose nephrotomography. Myelolipomas are suggested by the presence of a relatively lucent mass displacing the kidney. A less common finding is tumor calcification [14,15]. Angiography may localize the mass to the adrenal gland and will demonstrate the degree of vascularity. Myelolipoma is an avascular tumor which distorts and displaces the adrenal vessels 1161.

Unlike functioning tumors of the adrenal gland, myelolipomas are not visualized by radioisotopes such as iodinated cholesterol derivatives [I 71. Roentgenography and intravenous pyelography may show a radiolucent suprarenal mass; however, gray scale ultrasonography is more sensitive than con- ventional roentgenography in detecting fat within the mass. A dense echogenic pattern is seen with these fatty tumors of the kidney and adrenal gland, but this is not specific for fatty tumors [14,18].

5ource Clinical

Presentation

Other Blood Medical Pressure

Problems (mm Hg) Body

Habitus

Surgical Procedure

and Incision

Dykman and Freedman

] 191 Parsons and

Thompson

191 Figueroa and

-Tedeschi

] 121 Engelking et al

NerzLn and Silen

I201 Whittaker

[271 Tulcinsky et al

1751 Olsson et al

[ 761

Gee et al [=I

Rubin et al

BeE!r et al

1741 Behan et al

1741 Snearly and

Ram [ 51 Pagana et al

Abdominal pain in right upper quadrant

Malaise, painful abdominal mass

Asymptomatic, found at cholecystectomy

Gross hematuria flank mass

Painful mass in right upper quadrant

Painful mass in left upper quadrant

Microscopic hematuria

Gross hematuria

Asymptomatic

Weakness, malaise

Rheumatic heart disease, renal calculus

Chronic osteomyelitis of toe

None

Flank pain None No

Dysuria, microscopic hematuria

Abdominal pain and weight loss

Back pain, malaise, hematuria

Coronary artery No disease mention

None 180170

None 18OIlOO

None 111/94 No mention Excision: thoracoabdominal

None 120/80 Obese Excision: transverse abdominal

None No mention

No mention

140190

No mention Excision: subcostal abdominal

Associated renal cancer

None

Obese

Robust

None 154198

200195

180190

Obese

Excision nephrectomy; thoracoabdominal

Excision, splenectomy, distal pancreatectomy; thoracoabdominal

Excision; subcostal abdominal

None Well nourished

Obese

178/118 Robust

Excision; abdominal flank with rib resection

Excision, radical nephrectomy and adrenalectomy; thoracoabdominal

Excision: transverse abdominal

Well nourished

Obese

Excision; thoracoabdominal

Excision; thoracoabdominal

No mention

Obese

Obese

Excision; no mention of incision

Excision and cholecystectomy; no mention of incision

Excision: transverse abdominal

284 The American Journal of Surgery

Myelolipoma of the Adrenal Gland

We believe that computed tomography is the most sensitive study in the evaluation of tumors of the adrenal gland, recognizing lesions as small as 1 cm. Improved resolution permits better recognition of tissue density. These density coefficients can be correlated with possible tissue types, allowing the diagnosis of myelolipoma to be strongly considered. However, lipoma, liposarcoma and fibrosarcoma cannot be differentiated with assurance.

It will become increasingly important to be aware of the existence and appropriate treatment of this tumor of the adrenal gland because it will be recog- nized more frequently with the expanded use of ul- trasound and computed tomography.

Therapy: Operation is necessary for both accurate diagnosis and relief of symptoms. Various incisions and operative procedures have been used in the treatment of myelolipoma. Radical excision is un- necessary. Simple excision is adequate. Exposure is gained through a transverse abdominal incision ex- tending to the flank. A thoracoabdominal incision is associated with a higher morbidity and is not rec- ommended. A posterior flank or “renal” incision is inferior because the abdominal viscera are inac- cessible to examination in the event the mass proves to be a malignant retroperitoneal tumor.

Summary

We report the 14th case of myelolipoma of the adrenal gland. Recommendations for appropriate diagnostic and therapeutic methods are made. Myelolipoma of the adrenal gland is a rare non- functioning tumor composed of lipoid and hemato- poietic elements. The most consistent complaint is abdominal pain caused by hemorrhage within the tumor. We identified an association with obesity and hypertension. Ultrasound combined with computed tomography is useful in diagnosis. With expanded use of these studies, myelolipoma will be recognized more frequently. Definitive diagnosis and treatment are accomplished by simple excision; radical surgery is unnecessary.

Addendum

Since submission of this manuscript, another report of a myelolipoma in a heterotopic adrenal gland was reported by Damjanov et al (Damjanov I, Katz S, Catalan0 E, Mason

D, Swartz A. Myelolipoma in a heterotopic adrenal gland. Cancer 1979;44:135@-6). Their patient presented with the nephrotic syndrome and was treated by surgical excision of the tumor along with partial nephrectomy.

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References

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