[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [General pathology](https://durgical.com/en/general-pathology/) › [Kidney](https://durgical.com/en/general-pathology/areas/kidney/) › Benign kidney tumours

# Benign kidney tumours

- Lesion

Three benign tumours matter: tiny papillary adenomas, fat-containing angiomyolipomas and brown oncocytomas that mimic cancer.

Updated Nov 12, 2026

## Key points

- Papillary adenoma: small (up to about 1.5 cm), well circumscribed, low-grade papillary cells.
- Angiomyolipoma: in a large share of patients with tuberous sclerosis (TSC1, TSC2, mTOR activation); risk of spontaneous hemorrhage.
- Angiomyolipoma cells are positive for melanocytic markers (HMB-45) and smooth muscle markers.
- Oncocytoma: tan to mahogany brown, central stellate scar; eosinophilic cells full of mitochondria.
- Oncocytoma is benign but must be told from chromophobe renal cell carcinoma.

## 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](https://durgical.com/en/conditions/tuberous-sclerosis-complex/) | 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.

## Memory aid

Fat, muscle and vessel in tuberous sclerosis; brown with a star-scar is the oncocytoma.

## 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.

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## Elsewhere in DurgiPedia

- [Benign vs malignant tumours: the comparison table](https://durgical.com/en/general-pathology/benign-vs-malignant-tumours-the-comparison-table/)

## Connections

## Related 3

- [Clear cell renal cell carcinoma](https://durgical.com/en/general-pathology/clear-cell-renal-cell-carcinoma/)
- [Papillary, chromophobe and the rarer renal cell carcinomas](https://durgical.com/en/general-pathology/papillary-chromophobe-and-the-rarer-renal-cell-carcinomas/)
- [Benign vs malignant tumours: the comparison table](https://durgical.com/en/general-pathology/benign-vs-malignant-tumours-the-comparison-table/)

## Related conditions 2

- [Tuberous sclerosis complex](https://durgical.com/en/conditions/tuberous-sclerosis-complex/)
- [Renal cell carcinoma](https://durgical.com/en/conditions/renal-cell-carcinoma/)

[← All of general pathology](https://durgical.com/en/general-pathology/)

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](https://medlineplus.gov/genetics/condition/tuberous-sclerosis-complex/) (MedlinePlus, US National Library of Medicine, 2025).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/general-pathology/benign-kidney-tumours/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/general-pathology/benign-kidney-tumours/