Adrenal gland & paraganglia

Adrenal cortical adenoma


Topic Completed: 1 November 2013

Minor changes: 8 April 2021

Copyright: 2003-2021,, Inc.

PubMed Search: Oncocytoma adrenal

Carmen Perrino, M.D.
Debra L. Zynger, M.D.
Page views in 2020: 2,445
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Cite this page: Perrino C, Zynger D. Oncocytoma. website. Accessed December 3rd, 2021.
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

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CT, right adrenal mass (arrow)

Left adrenal mass (arrow)

Left retroperitoneal
mass and right
adrenal mass
with fat

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

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

Admixed oncocytes,
adipocytes and

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

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Cytoplasm filled with mitochondria

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