Adrenal gland and paraganglia
Adrenocortical adenoma

Author: Carmen Perrino, M.D. (see Authors page)

Editor: Debra Zynger, M.D.

Revised: 20 January 2016, last major update November 2013

Copyright: (c) 2003-2016,, Inc.

PubMed Search: Oncocytoma adrenal
Cite this page: Oncocytoma. website. Accessed May 22nd, 2018.
Definition / general
  • Adrenal cortical adenoma comprised of cells with abundant eosinophilic cytoplasm
  • Debate over amount of oncocytic cells (predominance versus entire lesion)
  • Synonyms:
    • Oncocytic adrenal cortical adenoma
    • Adrenal cortical oncocytoma
  • Epithelial tumor arising from one of the 3 layers of adrenal cortex
  • Further details regarding development of oncocytosis not well understood
Clinical features
  • Cases usually diagnosed incidentally, most are non-functioning
  • Must be comprised of mostly oncocytic cells, debate over exact quantity
Radiology description
  • Adrenal gland mass best visualized on CT or MRI
  • Features helpful for differentiating adrenal oncocytic neoplasms from adrenal adenomas (AJR Am J Roentgenol 2011;196:592):
    • CT: inhomogeneous appearance, increased attenuation, fat poor
    • MRI: loss of signal intensity on opposed-phase MR images, fat poor
  • No features can reliably distinguish benign from malignant adrenal oncocytic neoplasms on imaging (AJR Am J Roentgenol 2011;196:592)
Radiology images

Images hosted on other servers:

CT, right adrenal mass (arrow)

Left adrenal mass (arrow)

Noncontrast CT, left adrenal mass with fat (arrow)

Right adrenal mass with fat and left retroperitoneal mass

Prognostic factors
  • Like all adrenal neoplasms, criteria are not well-established to differentiate benign from malignant cases
  • Weiss System (Am J Surg Pathol 1984;8:163): most widely used criteria, but does not pertain to adrenocortical oncocytic neoplasms since many are classified as "malignant" but behave in benign manner
    • Criteria (≥3 criteria indicates malignancy): high mitotic rate, atypical mitoses, high nuclear grade, low percentage of clear cells, necrosis, diffuse tumor architecture, capsular invasion, sinusoidal invasion, venous invasion
  • Modified Weiss System (Am J Surg Pathol 2002;26:1612): >5 mitoses per 50 high powered fields, <25% clear cells, atypical mitotic figures, necrosis, and capsular invasion
    • Calculation:
      • 1 point each for the presence of atypical mitotic figures, necrosis, and capsular invasion
      • 2 points each for the presence of >5 mitoses per 50 high powered fields and <25% clear cells
      • Total score ranges from 0 to 7, and score of >3 highly correlates with subsequent malignant behavior
    • Certain modified Weiss features, specifically the presence of clear cells, may not be applicable to eosinophilic adrenal neoplasms
  • Modified Weiss System for adrenocortical oncocytic neoplasms (Int J Surg Pathol 2004;12:231): an additional scoring system specifically proposed for oncocytic adrenocortical tumors
    • Major criteria (presence of any indicates malignancy): high mitotic rate (>5 mitoses per 50 high power fields), atypical mitoses, venous invasion
    • Minor criteria (presence of any indicates uncertain malignant potential): large size (>10 cm or >200 gm), necrosis, capsular invasion, sinusoidal invasion
  • Other gross features which have been correlated with behavior include adrenal gland weight and tumor size (Am J Surg Pathol 2002;26:1612)
    • Benign tumors typically weigh <50 grams, malignant tumors >100 grams, and tumors that are >500 grams are likely to be malignant
    • Tumors measuring ≥6.5 cm are likely to be malignant
Case reports
  • Adrenalectomy (laparoscopic or open)
Gross description
  • Well-circumscribed, adrenal cortical lesion
  • Dark tan to mahogany brown (similar to other oncocytic lesions)
  • Size: 3 - 15 cm
  • Weight: 30 - 865 gm
Gross images

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Red-tan lobulated surface with attached adipose tissue

Tan, solid oncocytoma with presumed adjacent aldosteronoma (black outline)

Microscopic (histologic) description
  • Architecture: nesting, alveolar, cords, trabeculae (similar to other adrenal cortical adenomas)
  • Polygonal cells with abundant granular, eosinophilic cytoplasm
  • Pleomorphic nuclei may be present
  • Low mitotic rate, no atypical mitotic figures
Microscopic (histologic) images

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Diffuse oncocytic cells

Alveolar nests of polygonal oncocytic cells

Tumor cells with abundant granular cytoplasm

Solid sheets of tumor cells with eosinophilic cytoplasm

Admixed oncocytes, adipocytes, and trilineage hematopoiesis

Strongly postive for Inhibin

Cytology description
  • Hypercellular, discohesive epithelioid cells in three dimensional loose aggregates/clusters or as single cells, abundant eosinophilic/granular cytoplasm, most nuclei are oval and hyperchromatic but there may be moderate nuclear pleomorphism and prominent nucleoli, cells cling to delicate arborizing capillaries (Acta Cytol 2010;54:627)
  • Presence of a minority of cells with clear cytoplasm is acceptable, cut-off not established but <25% of tumor cells has been proposed (Acta Cytol 2010;54:627)
Positive stains
  • Frequently positive: synaptophysin, inhibin, NSE, vimentin, MelanA
  • Sometimes positive: cytokeratin (CK8, CK18, AE1/AE3), calretinin
  • Rarely positive (few reported cases): CD10, EMA, CAM5.2 (Hum Pathol 2011;42:489)
Negative stains
  • Negative: chromogranin (positive in adrenal medulla), CAM 5.2, EMA, S100, HMB45, CD10
  • Low Ki-67 proliferation index
Electron microscopy description
  • Cytoplasm contains compactly arranged mitochondria with vesicular, tubular, and lamella cristae, as well as occasional intramitochondrial inclusions (Am J Surg Pathol 1991;15:949)
Electron microscopy images

Cytoplasm filled with mitochondria

Molecular / cytogenetics description
  • Very few cases have been reported, therefore the molecular/cytogenetic abnormalities are not well defined