Myelolipoma of the : Case report and review of the literature

RICHARD A. SCHELLIN, D.O. Fort Worth, Texas

dentally via CT, especially when scanning was is a rare, benign, performed for an unrelated problem. 8 With the in- nonfunctioning of the creased use of the newer high-resolution, thin-sec- adrenal gland and consists of fatty tion scanners, undoubtedly more asymptomatic, and hematopoietic tissue. It is usually benign adrenal lesions of even smaller size will be found only at autopsy; the present discovered. patient represents only the 33rd This report presents the 33rd reported clinical reported clinical case of the tumor. case of adrenal myelolipoma, as well as a review of The clinicoradiologic features of the literature regarding its clinicoradiologic diag- myelolipoma are described, and it is nosis and treatment. expected that with the wider application of newer computed Report of case tomographic scanners, more tumors A 40-year-old white woman was admitted for evaluation of this nature will be encountered in of global weakness, aphasia, vertigo, amnesia, and a clinical cases. Because it is usually an near syncopal episode. She had been experiencing ce- phalalgia for the past week and stated that that was ex- asymptomatic, incidentally found, tremely unusual for her. Her past medical history in- nonmalignant tumor, it is important cluded questionable hypoglycemia and two episodes of for the radiologist to include it in acute labyrinthitis, the most recent being 6 months pri- differential diagnosis, especially or to this admission. when computed tomography Physical examination revealed an obese woman with demonstrates a fat-containing tumor. a supine pressure of 140/80 mm. Hg. There was Criteria of benign versus malignant questionable muscle weakness of the left upper extrem- adrenal lesions are also presented. ity. Pale striae of the abdomen were also noted. No other Percutaneous biopsy is physical signs were identified. Usual admission labora- recommended when the diagnosis is tory test results were normal. Electroencephalographic doubtful. should be reserved and brain CT scanning findings also were normal. only for definite malignancy or During her hospitalization, the patient was noted to have labile , with the diastolic pressure ris- questionable biopsy cases. In ing to 110 mm. Hg. Intravenous pyelography demon- agreement with other authors, a strated normal renal function and a right suprarenal conservative management approach mass of low density measuring 6 cm. in diameter (Fig. in questionable cases, especially in 1). Some amorphous calcification was noted along the elderly patients who cannot tolerate medial margin of the mass, and the mass appeared to be surgery, is also presented. flattening the superior pole of the right . Ultra- sonography was performed, and it revealed a 5 x 6-cm. right adrenal mass with an echodense pattern through- out. At its medial margin, hard echoes with associated shadowing indicated the presence of calcification. The overall pattern was consistent with a fatty tumor con- taining calcification (Fig. 2). Myelolipoma is a rare, nonfunctioning, benign tu- Adrenal CT showed a 6 x 6-cm. hypodense mass of the mor of the adrenal gland and consists of adipose right adrenal gland. The mass was homogeneous, and tissue and hematopoietic elements. 1 2 Most of while no specific density numbers were obtained, it ap- these tumors are described at autopsy as inciden- peared slightly more dense than adjacent retroperito- tal findings. A small number have been discovered neal fat. Calcification along the medial margin was again clinically and resected. seen (Fig. 3). Some small (1 cm.) left para-aortic nodes were also noted. The appearance was thought to be most Computed tomography (CT) has become the di- consistent with adrenal carcinoma with necrosis or with agnostic modality of choice for imaging the adren- . A myelolipoma was not considered al glands." Adrenal masses have been found inci- in the differential diagnosis.

Myelolipoma of the adrenal gland 26/63 neovascularity or tumor blush (Fig. 4). A simple right adrenalectomy was performed; it revealed a yellow to reddish-brown, homogeneous fatty tumor containing some hard foci of calcification. Microscopic examination showed a well-delineated but unencapsulated tumor with an adjacent rim of cortical tissue. The mass was composed of mature adipose tissue and hematopoietic elements. Foci of calcification and a focus of osseous met- aplasia were also noted. Final diagnosis was adrenal myelolipoma. The patients postoperative course was uneventful. She is being followed for her labile hyper- tension.

Discussion Fig. 1. A tomographic cut of kidneys shows a low-density mass Patients ages at time of discovery range from 17 to above the right kidney, which causes some flattening of the supe- 93 years9; the majority of symptomatic cases oc- rior pole. Amorphous calcification is present within the mass at its medial aspect. curred between the fourth and seventh decades39- 12 No sex predilection was found by some authors,9" 11 while other investigators reported a 1.75:1 to 2:1 male to female predominance.212

Pathology Myelolipoma is usually a circumscribed tumor of the or medulla. 19 The tumor is re- ported as an incidental autopsy finding in 0.2 to 0.8 percent of cases. 11,13-15 Size of the tumor varies from a few millimeters to 8 cm. in autopsy cases, 11 "6 while symptomatic resected tumors vary from 6 cm. and 50 gm. 11 to 30-34 cm. and 5,500-5,900 gm. 1,12 A myelolipoma is composed of mature fat and tissue in varying amounts. Certain authors report the presence of a capsule, 13•14 while others describe no capsule. Most reports state that the tumor is well-circumscribed or encapsulated, but on microscopic evaluation they describel91315 a pseudocapsule of adjacent compressed adrenal cortical tissue, as was present in the reported case. In other areas of the tumor, some collagen layers are seen between the interface of the mass and normal cortical tissue. Some areas reveal fibrosis with fat necrosis and hemorrhage, thus indicating 1,15 Figs. 2A and 2B. Longitudinal ultrasonograms reveal echogenic infarction ; hemorrhage was usually found in mass between the right kidney and the . The echogenic pat- symptomatic tumors. 15 Calcification in areas of tern is the same as the retroperitoneal fat located posterior to the kidney. In Fig. 2B, note the two hard echoes at the anterior sur- hemorrhage was also described.1415 face of the mass, with apparent acoustic shadowing suggesting the presence of calcification within the mass. Etiology The cause of adrenal myelolipomas still is un- known. The following possibilities have been pro- posed: (1) embryonic rests of primitive mesenchym- al tissue; (2) emboli of bone marrow cells; and (3) Samples were obtained for serum and urinary testing, and the patient metaplasia of adrenocortical cells in response to was allowed to go home. These endocrine determina- some still unknown stimulus3 9-1517 The last the- tions were found to be normal, and she was readmitted 2 ory is the most widely supported. Multiple reports 2,10-13,17 weeks later for angiography and exploratory surgery. have suggested that the stimulus for the Angiography revealed a hypovascular, 6-cm. right ad- metaplasia may be associated with systemic renal mass with calcification, but without evidence of from chronic illnesses or necrotic tissue.

27/64 Jan. 1986/Journal of AOA/vol. 86/no. 1 Clinical features As earlier stated, most myelolipomas are asymp- tomatic and are incidental discoveries. Of the symptomatic cases reported, most patients were obese or were described as robust or well nour- ished. The majority also had high blood pres- sure.1,2,12 Our patient was obese and had labile hy- pertension. In fact, evaluation of her hypertension led to the discovery of the adrenal mass. The most common presenting complaint was abdominal pain; this is believed to be due to hemorrhage within the tumor. 15 Hematuria is another fairly common finding, but its association with myeloli- poma is unclear. Noble and associates suggest that the hypertension and hematuria are probably not related to the myelolipoma. In almost all cases, endocrinologic work-up has revealed no endocrine function of the tumor. Our case further supports this finding. Bennett and co- workers 7 reported a single case of functioning myelolipoma. His paper describes a large myeloli- poma that was found in a previous subtotal adren- alectomy site of Cushings disease. The patient had a recurrence of his cushingoid symptoms, and the myelolipoma was found to have collections of adrenocortical cells disbursed throughout rather than a rim of cortical tissue. Radiographic studies Plain radiography of the abdomen usually is not helpful in demonstrating myelolipoma. Sometimes Fig. 3A. Computed tomogram just superior to the kidneys reveal a radiolucent mass or a mottled appearing mass a smoothly marginated 6 x 4-cm. hypodense mass of the right adrenal gland. Calcification of the anteromedial margin of the can be seen in the areas of the kidney. s If the mass mass is present. The density of the mass is just slightly greater contains calcification, this also may be identified. than the adjacent retroperitoneal fat and is quite homogeneous These findings are not definitive, however. Usual- except for the calcified margin. Fig. 3B. A more caudal cut re- veals the relationship of the mass to the liver and the right kid- ly, nephrotomography will be helpful in screening ney. A fleck of calcium is seen along the anterolateral margin of for an adrenal tumor. A radiolucent or soft-tissue the adrenal mass. The density of the mass appears more hetero- mass along with calcification is better visualized geneous, but its center is still only slightly greater than fat. on tomographic cuts of the kidney. The kidney may also appear displaced inferiorly or laterally, which suggests the presence of an adrenal mass. However, both plain film radiography and urogra- phy with tomography are able only to detect ad- ance characteristic of myelolipomas, they do feel renal masses larger than 2.5 cm.5 that the dense echographic appearance is charac- Ultrasonography has been used to screen for ad- teristic of fat, resembling the echographic appear- renal masses, but it has been found to be too insen- ance of retroperitoneal fat. They further conclude sitive.4 The examination is technically difficult for that ultrasonography in combination with other the sonographer to perform, and the results are ex- radiographic findings, especially computed tomog- tremely dependent upon his/her expertise. Echog- raphy and angiography, greatly enhance the speci- raphy is, however, quite helpful in distinguishing ficity for a correct preoperative diagnosis. whether a mass is solid or cystic. It is also quite Computed tomography has rapidly replaced oth- sensitive and reliable in determining the fatty con- er imaging modalities as the procedure of choice tent of a tumor. Both Scheible and coauthors s and for detecting adrenal pathology. 3-615 It has the Behan and associates is have described the very ability to accurately recognize adrenal tumors as dense echogenic nature of myelolipomas. While small as 1 cm. 15 With the wider use of newer high- neither group considers the sonographic appear- resolution, thin-section scanners, CT will probably

Myelolipoma of the adrenal gland 28/65 or tumor blush is seen." Its benign vascular ap- pearance plus its radiolucency with or without cal- cification should bring myelolipoma to mind.14 However, angiography cannot differentiate a mye- lolipoma from a retroperitoneal lipoma. 16 Angiog- raphy also is associated with an 8 percent chance of morbidity and adrenal gland infarction. The vascularity can actually be evaluated by CT en- hancement, obviating the need for angiography and its attendant risks." As previously stated, CT is not definitive in pre- dicting histology. A fatty tumor such as a myeloli- poma can be strongly suspected, but the diagnosis is not pathognomonic. Glazer and associates re- ported on nonfunctional adrenal masses that were incidentally discovered on CT. Myelolipomas were specifically excluded from their study, but they re- ported on benign . They found malignan- cy to be unlikely in adrenal masses measuring less than 3 cm. The study discovered adrenal tumors at an earlier or smaller size than most other reports where the adrenal lesions were primarily discov- ered by excretory urography. In a similar study on Fig. 4. A selective right renal arteriogram shows the inferior incidentally found adrenal masses on CT examina- right adrenal artery supplying the mass. The adrenal artery is tions, Mitnick and coworkers proposed certain seen draping around the inferior and medial aspect of the tumor. criteria as evidence of benignity. Differentiation No neovascularity or tumor blush was identified. by CT is based on the growth pattern. They pro- posed the following criteria for benign lesions: smooth round or oval contour of lesion; well-delin- eated tumor margin; tumor size less than 5.0 cm.; be able to detect even smaller lesions of the adren- and no growth on serial scans at 3, 6, and 12 al glands. CT is also extremely sensitive in detect- months. Certain other findings, such as calcifica- ing the presence of fat within a mass. Based upon tions, decreased attenuation, or contrast enhance- negative CT density numbers, most of the myeloli- ment, were present in both benign and malignant pomas evaluated with CT have reported the pres- tumors. They did state that when these findings ence of fat within the mass.2,4-6,9,15,16,19,20 While are present, it may be an indication for closer fol- most of these authors reported the presence of fat, low-up scans. they also noted heterogeneous density of the mass. Most of the clinically symptomatic patients un- The density varied with the amount of fat relative derwent surgery because malignancy was suspect- to soft tissues. Consequently, CT can be highly ed. In the majority of reported cases to date, myelo- suggestive of a fat-containing tumor, but it is not lipoma was not considered preoperatively, as was pathognomonic for myelolipoma, especially when true in the reported case. greater amounts of soft tissue densities are pres- Considering that CT is more widely available to- ent.9"6-25 It cannot differentiate between myeloli- day and that newer scanners with higher resolu- poma, liposarcoma, lipoma, or fibrosarcoma.15 tion are now in use, it is reasonable to assume that Further limitations occur in computed tomog- incidental adrenal lesions will be found and inves- raphy when the tumor is very large, because it tigated more frequently. It is also reasonable to ex- may be difficult to determine from which organ the pect that the lesions will be found at an earlier mass originates." The CT image can also be ex- stage or a smaller size. Endocrine evaluation of tremely difficult to interpret when there is a pauci- these lesions does not rule out the possibility of ty of surrounding retroperitoneal fat, as in a thin malignancy. It has been documented that the in- person, or when motion artifacts are present.3 cidence of adrenal nodules increases with age and Angiography is also useful in preoperative diag- that overall nodules are quite common. It also nosis. It helps to localize the mass to the adrenal seems reasonable that a greater frequency of be- gland. A myelolipoma is angiographically hypo- nign, nonfunctioning tumors, including myelolipo- vascular to avascular. 3,9,14,16,19 No neovascularity mas, will be discovered. The radiologist will, there-

29/66 Jan. 1986/Journal of AOA/vol. 86/no.1 fore, need to become familiar with the various tumoral pathology of the adrenal glands. J Comput Assist Tomogr 4:71- 7, Feb 80 benign tumors and their characteristic findings in 7. Glazer, H.S., et al.: Nonfunctioning adrenal masses. Incidental dis- order to eliminate unnecessary surgery with its at- covery on computed tomography. AJR 139:81-5, Jul 82 tendant risks. 8. Prinz, R.A., et al.: Incidental asymptomatic adrenal masses detected by computed tomographic scanning. Is operation required? JAMA 248:701-4, 13 Aug 82 Conclusion 9. Liebman, R., and Srikantaswamy, S.: Adrenal myelolipoma demon- strated by computed tomography. J Comput Assit Tomogr 5:262-3, Apr Application of the previously mentioned criteria 81 for benign lesions in general and myelolipomas 10. Filobbos, S.A. and Seddon, J.A.: Myelolipoma of the adrenal. Br J specifically will lead to greater recognition and di- Surg 67:147-8, Feb 80 11. Ayyat, F., et al.: Myelolipoma of the adrenal gland. Urology 16:415- agnosis. Because most lesions will be small and 8, Oct 80 asymptomatic, serial scanning with CT and ultra- 12. Wilhelmus, J.L., et al.: Giant adrenal myelolipoma. Case report and sonography will be all that is required to prove review of the literature. Arch Pathol Lab Med 105:532-5, Oct 81 13. Fernandez-Sanz, J., et al.: Adrenal myelolipoma simulating a retro- that the lesions are benign. With questionable tu- peritoneal malignant neoplasm. J Urol 126:780-2, Dec 81 mors, percutaneous biopsy under CT guidance 14. Rubin, H.B., Hirose, F., and Benfield, J.R.: Myelolipoma of the ad- would appear to be a reasonable alternative to sur- renal gland. Angiographic findings and review of the literature. A M J Surg 130:354-8, Sep 75 gery to confirm histology. If the diagnosis remains 15. Pagana, T.J., et al.: Myelolipoma of the adrenal gland. Am J Surg in doubt following biopsy and the mass is greater 141:282-5, Feb 81 than 5 cm., simple surgical excision should prob- 16. Behan, M., et al.: Myelolipoma of the adrenal gland: Two cases with ultrasound and CT findings. AJR 129:993-6, Dec 77 ably be performed, especially in the younger pa- 17. Bennett, B.D., et al.: Adrenal myelolipoma associated with Cush- tient. This management approach is in agreement ings disease. Am J Clin Path 73:443-7, Mar 80 with both Prinz and associates" and Mitnick and 18. Scheible, W., et al.: Lipomatous tumors of the kidney and adrenal. Apparent echographic specificity. Radiology 129:153-6, Oct 78 coauthors. 21 In the older patient who would not 19. Fink, D.W., and Wurtzebach, L.R.: Symptomatic myelolipoma of the tolerate surgery as well, serial scanning at 1-2 adrenal. Report of a case with computed tomographic evaluation. Radi- month intervals should prove beneficial as follow ology 134:451-2, Feb 80 20. Lamki, N., et al.: CT appearance of adrenal myelolipoma. CT 6:30-1, up. Apr 82 21. Mitnick, J.S., et al.: Nonfunctioning adrenal adenomas discovered incidentally on computed tomography. Radiology 148:495-9, Aug 83

1. Noble, M.J., Montague, D.K., and Levin, H.S.: Myelolipoma. An un- usual surgical lesion of the adrenal gland. 49:952-8, 1 Mar 82 2. Ishikawa, H., et al.: Myelolipoma of the adrenal gland. J Urol Accepted for publication in June 1985. Updating, as necessary, 126:777-9, Dec 81 has been done by the author. 3. Curtis, J.A., Brennan, R.E., and Kurtz, A.B.: Evaluation of adrenal disease by computed tomography. Comput Tomogr 4:165-8, Jul-Sep 80 Dr. Schellin is an attending radiologist and director of nuclear Hattery, R.R., et al.: Computerized tomography of the adrenal gland. 4. magnetic resonance section at Fort Worth Osteopathic Hospi- Semin Roentgenol 16:290-300, Oct 81 tal, Fort Worth, Texas. 5. Karstaedt, N., et al.: Computed tomography of the adrenal gland. Ra- diology 129:723-30, Dec 78 Dr. Schellin, Fort Worth Osteopathic Hospital, 1000 Montgom- 6. Eghrari, M., et al.: The role of computed tomography in assessment of ery Street, Fort Worth, Texas 76107.

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