Renal oncocytoma

Renal oncocytoma is a benign kidney tumour that is removed to exclude malignancy.

General

• Can be difficult to distinguish radiologically from RCC (chromophobe subtype).
  • ... and pathologists occasionally struggle like the radiologists.
• Benign tumour - the reason it is excised is... one cannot be certain it isn't a RCC.

Gross

• Brown, mahogany brown.
• 1/3 have a characteristic central scar.

Image

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  Renal oncocytoma with central scar. (WP)

Microscopic

Features:

• Eosinophilic cytoplasm - slightly granular key feature.
• Cells arranged in nests.
• Nuclei uniform and round.
  • Slightly enlarged nuclei, but no significant pleomorphism (size variation) - important.

Notes:

• May look like eosinophilic variant of chromophobe RCC -- this is the main DDx.
  • A comparison based on histomorphology: Tabular comparison between ChRCC & oncocytoma.
    • Oncocytoma typically has: no perinuclear clearing, no raisinoid nuclei, no binucleation.

DDx:

• Chromophobe renal cell carcinoma, eosinophilic variant.
• Clear cell renal cell carcinoma, eosinophilic variant.

Images

• 

  Oncocytoma - high mag. (WC/Nephron)

• 

  Oncocytoma - intermed. mag. (WC/Nephron)

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  Oncocytoma - low mag. (WC/Nephron)

Stain=

• Hale's colloidal iron -ve
  • ChRCC +ve (blue granular cytoplasmic).

IHC

• CK7 -ve/+ve (cytoplasmic) .
  • Chromophobe renal cell carcinoma = cell membrane +ve.

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PORTION OF KIDNEY, RIGHT, PARTIAL NEPHRECTOMY:
- ONCOCYTOMA.

Micro

The sections show a tumour with cells arranged in nests. The tumour cells have abundant eosinophilic cytoplasm. The tumour cell nuclei are round and have round nucleoli. No perinuclear halos are apparent. Binucleation is not apparent. No zonal necrosis is identified. Focally, tumour nests are spaced reminiscent of an archipelago. Mitoses are not apparent. The tumour is moderately circumscribed.

The thin rim of renal parenchyma has no apparent pathology on the H&E stained sections.

See also

• Kidney tumours.
• Oncocytoma.