[Outcome of oncocytomas diagnosed by percutaneous renal biopsy]

Renal oncocytoma is a benign tumour that is usually diagnosed postoperatively. Its natural history is poorly defined. We studied the outcome of patients with renal oncocytoma diagnosed by percutaneous biopsy and not operated.

From January 1998 to April 2004, on a series of 148 renal tumour biopsies performed in our centre, 15 showed oncocytoma. The initial treatment was non-surgical. We report the follow-up of these patients and the course of these oncocytomas. The mean follow-up was 404 +/- 20.9 months.

The mean age of these patients at diagnosis was 57.6 +/- 14.4 years and the mean tumour diameter was 3.49 +/- 2.43 cm with a mean volume of 62.3 +/- 135.4 cm3. Six of these 15 patients were operated: 4 total nephrectomies and 2 partial nephrectomies. The indications for surgery were the initial tumour volume (n = 1), tumour growth > 0.5 cm/year (n = 4) and the patient's preference (n = 1). Operated patients were younger (45.5 +/- 11.1 years vs 65.6 +/- 10.3 years) and had larger tumours at diagnosis (50 +/- 30.1 mm vs 27.3 +/- 10.5 mm). All 9 patients treated by watchful waiting were asymptomatic.

The natural history of oncocytomas appears to be a more or less rapid increase in size. Treatment can be conservative. The initial tumour volume or rapid tumour growth are indications for resection. Partial nephrectomy, when allowed by the size and site of the tumour is currently the technique of choice.