Benign kidney tumours
- Lesion
Three benign tumours matter: tiny papillary adenomas, fat-containing angiomyolipomas and brown oncocytomas that mimic cancer.
What it is
Papillary adenomas are small cortical nodules found often at autopsy; they share trisomies 7 and 17 with papillary renal cell carcinoma and are separated from it by size. Angiomyolipoma, a tumour of perivascular epithelioid cells (PEComa) with fat, smooth muscle and thick-walled vessels, is common in tuberous sclerosis and can bleed. Oncocytoma arises from intercalated cells of collecting ducts and is packed with mitochondria.
Structure
- Papillary adenoma: pale yellow-grey cortical nodule made of papillae lined by bland cuboidal cells.
- Angiomyolipoma: yellow fatty tumour with mature fat, spindle and epithelioid smooth muscle, and thick dysmorphic vessels.
- Oncocytoma: homogeneous brown tumour with a central scar; nests of round cells with granular pink cytoplasm and small round nuclei.
Benign renal tumours
| Tumour | Associations | Key features |
|---|---|---|
| Papillary adenoma | Aging, end-stage kidneys | Small papillary nodule; trisomy 7 and 17 |
| Angiomyolipoma | Tuberous sclerosis | Fat, smooth muscle, vessels; HMB-45 positive; bleeding |
| Oncocytoma | Sporadic; rarely familial | Brown, central scar, mitochondria-rich cells |
Clinical notes
- Large angiomyolipomas can rupture and cause retroperitoneal hemorrhage, especially in pregnancy.
- Imaging cannot reliably separate oncocytoma from carcinoma, so many are removed.
Test yourself
Think of the answer, then tap the question to see it.
Which genetic syndrome is associated with renal angiomyolipomas?
Tuberous sclerosis complex (TSC1 or TSC2).
What gives the oncocytoma its pink granular cytoplasm?
Abundant mitochondria.
Which malignant tumour can mimic oncocytoma?
Chromophobe renal cell carcinoma.
Elsewhere in DurgiPedia
Connections
Educational content on the mechanisms of disease; not a diagnostic or treatment guide and no substitute for a health professional's advice. No doses are given.
Sources: Tuberous sclerosis complex: MedlinePlus Genetics (MedlinePlus, US National Library of Medicine, 2025).
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Representative model, for educational purposes only.