Hybrid tumour ‘oncocytoma‐chromophobe renal cell carcinoma’ of the kidney: a report of seven sporadic cases

OBJECTIVES To determine whether renal hybrid tumours (HT) appear as a specific clinical and radiological entity, as HT are characterized by the association of both oncocytes and chromophobe cells within the same tumour, and have been described in patients with oncocytosis and Birt‐Hogg‐Dube syndrome. PATIENTS AND METHODS We reviewed the medical charts of 67 patients who had a partial or radical nephrectomy in our institution for renal oncocytoma (RO, 24), chromophobe renal cell carcinoma (CRCC, 36) and HT (seven), from January 2006 to October 2007. We report the clinical, radiological and pathological characteristics of the seven cases of HT. RESULTS The mean (range) age of the patients was 56 (41–68) year. None of the seven patients had any suspicion of RO, based on computed tomography (CT). Two patients had a history of kidney cancer. Five patients had partial and two a radical nephrectomy. The mean (range) maximum tumour diameter was 5.5 (1.8–9) cm. Two tumours were pT1a, two were pT1b and three were pT2. Pathological analysis showed RO‐like and CRCC‐like cells intermixed (six patients) or distinct (one). After a median (range) follow‐up of 20 (8–25) months, none of the patients had any evidence of disease recurrence. CONCLUSIONS In a large series of patients with sporadic RO and CRCC, 10% of the tumours had hybrid morphological features, as described in oncocytosis and Birt‐Hogg‐Dube syndrome. We were unable to identify any specific clinical characteristic. Most importantly, none of these HT showed any of the radiological characteristics of RO.