Renal oncocytoma: a clinicopathological analysis of 45 consecutive cases

OBJECTIVE To evaluate the clinical behaviour and pathology of renal oncocytoma in a well-defined population over a 30-year period. PATIENTS AND METHODS In a retrospective population-based study we assessed relevant clinical and pathological factors in 45 patients (31 men and 14 women) diagnosed with renal oncocytoma in Iceland between 1971 and 2000. Clinical presentation, pathology, survival and causes of death were evaluated. RESULTS The age-standardized incidence was 0.3 per 100 000 per year for both men and women, the incidence of oncocytomas being 5.5% of renal cell carcinomas (RCCs) diagnosed during the same period in Iceland. Fourteen patients were diagnosed at autopsy for an unrelated disease. Of 31 living patients (mean age 70.5 years), seven were diagnosed incidentally (23%), and the others had presented with haematuria (32%), abdominal pain (29%), and weight loss (10%). All the patients had a radical nephrectomy, except for one with bilateral oncocytoma who had a partial nephrectomy. The mean (range) tumour size was 5.7 (0.9-12) cm. Eighteen patients (58%) were diagnosed at Tumour-Node-Metastasis stage I, 10 at stage II (32%) and three at stage III (10%), all of those at stage III having renal capsular penetration or tumour invasion into perirenal fat tissue (T3aN0M0). No patients were diagnosed with lymph node or distant metastasis. Two cases of coexisting RCC were detected. After a median follow-up of 8.3 years there were no recurrences or deaths from oncocytoma (100% disease-specific survival). The overall 5-year survival was 63%, with most patients dying from cardiovascular diseases or nonrenal cancers. CONCLUSIONS In most cases renal oncocytoma behaves like a benign tumour; the long-term prognosis is excellent. Thus, in the present patients, radical nephrectomy could be regarded as an over-treatment and nephron-sparing surgery as more appropriate, especially in patients with small tumours. However, both coexisting RCC and perirenal fat invasion, a hallmark of malignant behaviour, might indicate that more radical surgery is warranted in some of these patients.