Year : 2008 | Volume
: 51 | Issue : 4 | Page : 531--533
Functional adrenal oncocytoma: A rare neoplasm
Nitin Sharma1, Prem Nath Dogra1, Sandeep Mathur2,
1 Department of Urology, All India Institute of Medical Sciences, New Delhi 110 029, India
2 Department of Pathology, All India Institute of Medical Sciences, New Delhi 110 029, India
Department of Urology, All India Institute of Medical Sciences, New Delhi 110 029
Adrenal oncocytoma is a rare adrenal neoplasm with only 21 cases reported in English literature. These adrenal tumors are usually nonfunctional and hence incidentally detected. Most of these adrenal neoplasms are benign. We report a rare case of adrenal oncocytoma that was functional and was successfully managed by laparoscopic adrenalectomy.
|How to cite this article:|
Sharma N, Dogra PN, Mathur S. Functional adrenal oncocytoma: A rare neoplasm.Indian J Pathol Microbiol 2008;51:531-533
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Sharma N, Dogra PN, Mathur S. Functional adrenal oncocytoma: A rare neoplasm. Indian J Pathol Microbiol [serial online] 2008 [cited 2020 May 28 ];51:531-533
Available from: http://www.ijpmonline.org/text.asp?2008/51/4/531/43751
Oncocytomas are neoplasms composed of cells with abundant eosinophilic granular cytoplasm packed with swollen mitochondria.  The term "oncocyte", first used by Hamperl  in 1950, describes large, highly eosinophilic, granular cells associated with a hurthle cell tumor of the thyroid gland. Oncocytomas can arise in several organs, including the kidney, thyroid, salivary glands, parathyroid, lung, pituitary gland and ovary. , Adrenal oncocytoma is a rare entity, with only 21 cases reported till date in English literature. ,, These adrenal tumors are usually nonfunctional and hence incidentally detected. Most of these adrenal neoplasms are benign.  We report a rare case of functional adrenal oncocytoma.
A 47-year-old female patient, a known hypertensive for the past 2 years was receiving regular treatment with amlodipine 5 mg, atenolol 50 mg and hydrochlorthiazide 12.5 mg. Her blood pressure was 164/88 mmHg. She had no postural hypotension, but had headache and palpitations. A physical examination was unremarkable; no features suggestive of Cushing syndrome (petechiae, abdominal striae) were noted. An ultrasound showed a 9.5x7.6x7 cm solid mass lesion of heterogenous echotexture with areas of cystic degeneration in the left suprarenal gland. A non contrast computed tomogram showed a 10x7x7cm well marginated, solid adrenal mass on the left side with multiple internal septae and hypodense areas. There were peripheral solid nodular areas. On giving contrast, there was enhancement of capsule, internal septae and peripheral solid component. Few non enhancing areas were present in the center [Figure 1]. No perilesional stranding was present. The mass was compressing the upper pole of the left kidney.
Baseline laboratory parameters were within normal limits. Serum cortisol, dehydroepiandrostenedione sulfate (DHEA-S) and adrenocorticotrophic hormones (ACTH) were within normal limits. The overnight dexamethasone suppression test was normal. However, 24 hrs urinary vanillyl mandelic acid (VMA) (7.2 mg), epinephrine (.1 mg), norepinephrine (1.2 mg) and dopamine (0.32 mg) were increased.
Based on the above findings, a differential diagnosis of pheochromocytoma adrenocortical carcinoma was made and a remote possibility of a large adrenal adenoma was kept in mind.
A laparoscopic left adrenalectomy was performed using the lateral transperitoneal approach. The mass was completely encapsulated and easily dissected from the superior pole of the left kidney. The post-operative recovery was uneventful.
A specimen of the left adrenalectomy weighed 230 gms and measured 12x8x8 cm. The capsule was intact. On cut section, a light brown colored tumor replaced the entire adrenal parenchyma. A few cystic areas were seen. There were no areas of hemorrhage or necrosis [Figure 2]. A microscopic examination revealed tumor cells arranged in sheets, nests and cords, separated by fibrovascular septae. Individual cells had an abundant granular, eosinophilic cytoplasm [Figure 3]. The nucleus was central, vesicular and had an inconspicuous nucleolus. Immunohistochemically, the tumor cells were focally positive for chromogranin and vimentin. Tumor cells were negative for p53 and the MIB 1 labeling index was 0.02%. Electron microscopy did not reveal the presence of neurosecretory granules but showed the presence of mitochondria. A diagnosis of adrenal oncocytoma was made.
At the 6-month follow-up visit, the patient was asymptomatic with normal blood pressure without any anti-hypertensive medication and normal biochemical parameters.
Incidentally detected adrenal masses are found in 1-2% of abdominal CT scans.  These adrenal "incidentalomas"  can be cortical adenomas, cysts, myelolipomas, ganglioneuromas, pheochromocytomas, adrenocortical carcinomas and adrenal metastases.
The most common adrenal incidentalomas  (in a patient without a known primary malignancy) are nonfunctioning cortical adenomas. A biochemical evaluation should be performed to differentiate nonfunctional from functional adrenal masses. All functional adrenal masses and lesions greater than 6 cm should be removed.
Oncocytic neoplasms are most commonly found in the kidney, thyroid and salivary gland. Adrenal oncocytomas are very rare. There is female predominance with a mean age of 46 years. These tumors are more common on the left side (1:2). Most of these tumors are nonfunctional and hence incidentally detected. Tumor size ranged from 3-15 cm; with a median of 8 cm. These oncocytomas are generally benign tumors; however, 1 case of adrenal oncocytoma with local invasion and distant metastases has been reported.  The Weiss system  is most popular for distinguishing benign from malignant adrenocortical neoplasm. Grossly these tumors are rounded, well-circumscribed and encapsulated. A cut section shows tan brown color with areas of hemorrhagic necrosis. Histologically, these tumors contain cells arranged in solid, tubular, papillary, or trabecular patterns.  Cells are strongly eosinophilic and granular, due to the presence of numerous mitochondria.  The pathogenesis of these tumors is still not known. Some of the oncocytomas might be tumors of mitochondria at the subcellular level.
In our case, the occurrence of a unilateral adrenal mass opens to several differential diagnoses. Nonfunctioning adenoma was considered unlikely as these are usually smaller than 5 cm.
Myelolipoma are large in size, well-encapsulated and have a inhomogenous structure. But in this case, the absence of fat like attenuation in the CT scan argued against it.
Adrenal carcinoma was considered in the differential diagnosis. These tumors do actually reach large dimensions, but distant spread is usually present as infiltration of adjacent structures.
Adrenal gland pheochromocytomas can be confused with oncocytoma. This distinction is possible in most of the cases based on clinical and biochemical parameters. However, rarely pheochromocytomas can have cells with eosinophilic cytoplasm resembling oncocytes. Immunohistochemical studies are helpful in distinguishing such cases as pheochromocytomas are positive for chromogranin A and other neuroendocrine markers.  Electron microscopic studies will reveal dense-core membrane-bound granules in the cells of pheochromocytomas.
In our case, a preoperative diagnosis was very difficult. Large tumor size and heterogeneous echotexture on imaging raised the doubt of adrenocortical carcinoma. Investigations revealed the functional nature of the mass. The patient had hypertension and mild elevation in 24 hr urinary catecholamines, both of which were corrected after surgery. Even immunohistochemistry showing cells positive for chromogranin granules and vimentin further raised the suspicion of an oncocytic pheochromocytoma.
Adrenal oncocytomas, although rare, should be considered in the differential diagnosis of large adrenal tumors. These tumors are usually considered benign and nonfunctional, however, the possibility of functional adrenal oncocytoma mimicking pheochromocytoma should always be considered. The assessment of their exact biologic behavior requires further studies.
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