Case report A 45-year-old male presented for elective surgery to

repair an enlarging ventral hernia. Past medical history was significant for diabetes mellitus and exploratory laparotomy for a bleeding peptic ulcer, 18 years prior. In addition to a well-healed midline abdominal incision, the physical ex-amination found a 4 x 3-cm midline ventral hernia. Nor-mal bowel sounds were elicited in a soft, nontender abdo-men. Laboratory tests were significant only for an elevated glucose, 192 mg/dl, compatible with the given history of diabetes.

During the initial operative procedure, an unexpected mass was felt below the transverse colon (Fig. 1). Unaware of its content and potential complications, an immediate

intraoperative consultation to surgical oncology was ob-tained, as well as an intraoperative sonogram. The recom-mendation was to not perform intraoperative tissue sam-pling at this time. Instead, the abdomen was closed and the patient was immediately escorted to the radiology depart-ment for a CT scan of the abdomen and pelvis to further assess the mass. CT images revealed huge multiseptated masses (Fig. 2) with predominantly macroscopic “fat” at-tenuation, occupying almost the entire abdomen and upper

RCR Radiology Case Reports | radiology.casereports.net 1 2015 | Volume 10 | Issue 2

Bilateral giant adrenal myelolipomas presenting as an enlarging ventral hernia: Radiologic-pathologic correlation and literature reviewNajeeb Crossley, BS; Mica Grantham, MD; Marie Fidelia-Lambert, MD; Andre Dureinckx, MD, PhD; Bryson Nicholson, MD; Lori Wilson, MD; and Bonnie C. Davis, MD

Adrenal myelolipomas are fat-containing tumors that are rare, usually small and unilateral, as well as as-ymptomatic. They can, however, occur bilaterally and enlarge significantly, resulting in clinical symp-toms. A middle-aged male presented with an enlarging ventral hernia that was attributed to giant bilat-eral adrenal myelolipomas. With a combined measurement of at least 20 x 15 cm, the size of the masses is one of the largest reported for this particular entity, to our knowledge.

Citation: Crossley N, Grantham M, Fidelia-Lambert M, Dureinckx A, Nicholson B, Wilson L, Davis BC. Bilateral giant adrenal myelolipomas presenting as an enlarging ventral henia: Radiologic-pathologic correlation and literature review. Radiology Case Reports. (Online) 2015;10(2);985.

Copyright: © 2015 The Authors. This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs 2.5 License, which permits reproduction and distribution, provided the original work is properly cited. Commercial use and derivative works are not permitted.

Mr. Crossley is an Assistant Professor in the Department of Radiology, and Dr. Davis is an Assistant Professor at Howard University College of Medicine, Washington DC. Dr. Grantham is in the Department of Pathology at Howard University Hospital. Dr. Fidelia-Lambert is in the Department of Pathology, Dr. Dureinckx is in the Department of Radiology, and Drs. Nicholson and Wilson are in the Department of Surgery, all at Howard University College of Medicine, Washington, DC. Contact Dr. Davis at bondav1843@msn.com.

Competing Interests: The authors have declared that no competing interests exist.

DOI: 10.2484/rcr.v10i2.985

Radiology Case ReportsVolume 10, Issue 2, 2015

Fig. 1. Giant adrenal myelolipoma in a 45-year-old male presenting for ventral hernia repair. Intraoperative image shows a large unexpected abdominal mass (white arrow) representing a segment of an adrenal myelolipoma that accounted for an enlarging ventral hernia.

pelvis. MRI showed complementary findings (images not shown). Based on imaging, the major contenders in the differential diagnosis, especially due to the large size of the mass(es), included predominantly fat-containing pri-mary adrenal and/or retroperitoneal masses such as bilateral myelolipomas, lipomas, lipo-sarcoma(s), bilateral exophytic angiomyolipo-mas, and teratoma(s), with metastatic disease (containing fat), rounding out the list. Strik-ingly, both kidneys were inferiorly displaced (Fig. 2) into the pelvis, while maintaining cor-tical continuity; this was an important finding that narrowed the differential possibilities to bilateral fat-containing suprarenal masses. During a followup surgical procedure, which also included a true cut biopsy, only predomi-nantly midline and left abdominal masses were resected due to excessive hemorrhage. Tissue samples were submitted to pathology for histological review. At a later date, the patient succumbed to cardiovascular complications, and an autopsy was ultimately performed. Microscopic ex-amination of representative sections from both suprarenal masses, as well as from the prior biopsy, revealed adipose tissue containing he-matopoietic cells showing tri-lineage hemato-poiesis (Fig. 3). These results, along with a tu-mor size greater than 10 cm, confirmed the diagnosis of giant bilateral myelolipomas.

Discussion Incidence and clinical presentationDue to their benign indolent nature, most ad-renal myelolipomas are discovered incidentally

(especially given the increased use of cross-sectional imag-ing modalities), or at autopsy, with an incidence of 0.03% to 0.2% (1). With the widespread use of noninvasive imag-ing, including ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI), incidental detection of myelolipomas is becoming more common, and they consti-tute up to 10-15% of incidental adrenal masses (2).

Adrenal myelolipomas are rare, usually small (less than 4 cm), and asymptomatic (70%) (1) tumors. They were first described by Gierke in 1905 (2, 3-5), and given the name “myelolipoma” by Oberling in 1929 (4). Myelolipomas, however, can occur bilaterally and/or enlarge significantly. Tumors weighing several kilograms have been reported (4, 6) and can result in clinical symptoms (from the size alone and/or mass effect) such as abdominal or flank pain, nau-sea, vomiting, or (as in our patient) a ventral hernia. Acute intratumoral or retroperitoneal hemorrhage (4) can occur spontaneously as these tumors enlarge. Though they are known as hormonally inactive tumors, symptoms from hormonal activity from a variety of associated endocrine disorders have been reported (for example, Addison’s dis-ease, Cushing’s syndrome, Conn’s syndrome, obesity, viril-

Bilateral giant adrenal myelolipomas presenting as an enlarging ventral hernia

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Fig. 2. Fat-containing retroperitoneal masses in a 45-year-old male presenting for ventral hernia repair.(A) Transverse, contrast-enhanced CT image through the abdomen shows multiple large well-encapsulated retro- (long white arrow) and intraperitoneal (long yellow arrow) masses, predominately composed of fat-attenuated tissue interspersed with enhancing septa. Masses occupy almost the entire central abdominal cavity, with anterolateral dis-placement and compression of bowel loops (arrowhead). The size and complexity of the fat-containing lesions prompted the initial diagnosis of liposarcoma with a differen-tial diagnosis of myelolipoma. (B) Sagittal and (C) coronal contrast-enhanced CT images illustrate inferior displace-ment of the kidneys (yellow stars; sagittal view of right kid-ney not shown) by large multiseptated fat-attenuated le-sions. The bilateral renal cortex is not violated (yellow ar-rowheads), suggesting a suprarenal component/origin such as bilateral myelolipomas. (D) Coronal view from same CT scan illustrates the largest component of the masses, 21 x 12 cm, extending from the thoracoabdominal junction to the mid pelvis. (Incidentally, the presenting ventral hernia was reduced intraoperatively, which occurred prior to imaging with CT; see history in case report.)

ism, and pseudo-hermaphroditism [3]). The associations with diabetes mellitus, hypertension, obesity, atherosclerosis, and malignancy have also been described (2, 5), and mye-lolipomas can also occur in the setting of burns (7).

Location and histologyMyelolipomas predominantly arise from the adrenal cor-

tex, with possible origin from the zona fasciculata layer (8), the middle of the three layers composing the adrenal cortex (outermost layer, Zona glomerulosa; innermost layer, Zona reticularis). These tumors, however, may exist in an extra-adrenal location in approximately 15% of the cases (5), including the presacral region, perirenal retroperitoneum, liver, stomach, mediastinum, and lung (3). They affect both males and females (ratio, 1.75:1), with a higher incidence in the fifth and sixth decades of life (6). When unilateral, these tumors show a predilection to the right side (right:left ratio, 3:2.1) (3). Again, the size is usually less than 4 cm, and they are considered “giant myelolipomas” when the diameter is greater than 10 cm (6).

Several theories have been proposed to explain the pathogenesis of this tumor, including the following: foci of extramedullary hematopoiesis, hyperplasia of myeloid cells misplaced during embryogenesis, or the result of a degen-erative process in hyperplastic or adenomatous glands (9). However, Meaglia and Schmidt proposed the most widely accepted theory, based on the existence of metaplasia of the reticuloendothelial cells of blood capillaries, located in the adrenal gland, in response to stimuli such as infection, necrosis, and stress (3).

Myelolipomas are composed of a mixture of mature adipose tissue and hematopoietic elements (10), including

some with calcifications. This explains the sometimes het-erogeneous appearance seen on imaging, though the classic presentations of small myelolipomas illustrate distinct ra-diographic findings on cross-sectional modalities. The im-aging features that distinguish this tumor are based on (a) the suprarenal location and (b) the fat content, with CT being the most sensitive of the modalities (2).

ImagingThe typical appearance of myelolipomas on CT imaging

is of a predominantly low-attenuated, well-encapsulated lesion with negative Hounsfield (HU) units corresponding to the “fat”-attenuated range (macroscopic fat with HU of -31 to -100 [11]). The larger masses more clearly show the interspersed, high-attenuated, myeloid components (as well as other tissue types included in the previously mentioned differential diagnosis). On MRI, the dominant content, fat, is hyperintense on T1-weighted images and loses signal on fat-suppressed, T1-weighted and -opposed phase se-quences. Sonographically, an echogenic mass appears due to the fatty content, though varying degrees of hypoecho-genicity may be represented due to the myeloid compo-nent. Thus, the imaging appearance of myelolipomas (that is, the degree of heterogeneity) depends on the relative proportion of macroscopic fat and myeloid present in the tumors (11).

In early reported cases of adrenal myelolipoma imaged with FDG-PET, usually no significant metabolic uptake was shown (12, 13). However, more recently, Ludwig et al (12) reported mixed metabolic activity in a myelolipoma, suggesting that the lack of activity corresponds to “necrotic and adipose” elements in the tumor, and that the presence of activity (that is, if the tumor is FDG-PET avid) corre-sponds to the “adenomatous and hematopoietic” elements.

When imaging results are equivocal, especially when the tumor is large and/or heterogeneous and interspersed with fat and denser nonfatty myeloid tissue on CT, then image-guided, fine-needle aspiration may be warranted. Further rendering the diagnosis unclear is the presence of calcifica-tions, seen in about 27% (2, 14) of myelolipomas, and tu-mor enhancement, which has been reported (15). Extra-adrenal myelolipomas may mimic extramedullary hemato-poietic tumors, especially since bone spicules have been reported (14).

Clinical managementThe management of adrenal myelolipomas should be

determined on an individual basis. Incidentally discovered, small, asymptomatic tumors with unequivocal radiological findings can be monitored, with no need for immediate surgical intervention (9), though close monitoring is advised in the event of unexpected growth and development of symptoms. Initial operative intervention is reserved for symptomatic patients (9), as was the case in this particular scenario, or for those patients with a large silent tumor that can produce life-threatening shock secondary to spontane-ous hemorrhage (9). However, Meyer and Behrend advo-cate surgery for tumor size greater than 10 cm because of

Bilateral giant adrenal myelolipomas presenting as an enlarging ventral hernia

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Fig 3. Light microscopy features of adrenal myelolipoma. Islands of hematopoietic tissue with conspicuous megakar-yocytes (black star) within residual adrenal cortical cells (black diamond), mature fat cells (arrowhead), and intersti-tial hemorrhage (black arrow) (hematoxylin-eosin stain; original magnification 200x).

the small but distinct risk of developing abdominal pain or life-threatening hemorrhage that may be associated with large myelolipomas (5). Again, CT-guided aspiration or biopsy can be done initially to confirm the diagnosis when-ever it is in doubt (9), though this procedure is not without risk of rupture and bleeding (16). In addition to the very rare complication of a spontaneous bleed (especially in the larger tumors), there are several reports in the literature of spontaneous rupture of adrenal myelolipomas (17). In such cases, as reported by V. G. Patel (5), surveillance can be accomplished with serial CT or ultrasound examinations. If surgical intervention is required, preservation of adrenal tissue is vital so as not to commit patients to a lifetime of steroid replacement (17). Though laparoscopic adrenalec-tomy is gaining widespread acceptance as the gold-standard technique for benign adrenal masses smaller than 5 to 7 cm, the literature cites successful outcomes with the laparo-scopic approach in larger lesions, provided that a good pre-operative diagnosis is done (with imaging and endocrine evaluation) (18, 19).

ConclusionWhile bilateral myelolipomas are usually small, unilateral

and asymptomatic, our reported case of giant bilateral myelolipomas is a unique appearance of this tumor, with an uncommon presentation as an enlarging ventral hernia. Incidentally, to the authors’ knowledge, cross-sectional im-aging is not required in the routine surgical evaluation of seemingly uncomplicated ventral hernias; however, physi-cians should be aware that an underlying unexpected mass may be the root cause, as illustrated in this presentation. In the setting of a small, unilateral, asymptomatic retroperito-neal tumor, CT imaging can quickly establish a supra-renal origin of the mass and identify “fat” content within the lesion, to render a diagnosis of myelolipoma. On the other hand, in the setting of larger (sometimes massive) “fat”-containing abdominal tumors that lack classical CT find-ings, histological confirmation (via image-guided percuta-neous biopsy) may be warranted to confirm the diagnosis of a giant myelolipoma (or other fat-containing adrenal or other retroperitoneal masses), as was necessary in this par-ticular scenario.

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Bilateral giant adrenal myelolipomas presenting as an enlarging ventral hernia

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