Renal oncocytoma: experience of Clinical Urology A, Urology Department, CHU Ibn Sina, Rabat, Morocco and literature review

Renal oncocytoma is a rare and benign renal tumor. Only few cases have been reported in Moroccan populations. In the present study, we report our experiences in the diagnosis, management and follow-up of this disease. We report on six cases of renal oncocytoma indentified between 1990 and 2008 in the urology department of "CHU Ibn Sina" in Rabat. These six cases are listed among 130 kidney tumors reported during the study period. We assess the clinical, radiological and therapeutic features of the patients and we review literature. Six cases of renal oncocytoma, representing 4.6% of all primitive kidney tumors treated in our institution during the study period. The mean age was 53 ±9.7 years (range 34 to 61 years). One patient was asymptomatic at presentation, five patients (83%) had flank pain and two (33%) had macroscopic hematuria. The tumor was right sided in 4 cases (66%) and left sided in 2 cases (33%). All patients underwent CT scan which showed, in three cases, a centrally located stellate area of low attenuation. The clinical suspicion of oncocytoma was made preoperatively in only 3 patients by imaging studies, but the suspicion of renal cell carcinoma persist and all patients were treated with radical nephrectomy. Definitive diagnosis was made in all cases postoperatively. All the tumors were well circumscribed but unencapsulated. The mean tumor size was 8,75±2,04 cm. Four patients were classified at stage pT2 and two at stage p T1. Most of the pathological features in our patients were typical of this entity. Predominant cell type was a typical oncocytoma with general low mitotic activity. No extension to peri-nephric fat tissue or lymphovascular invasion was observed. After a mean follow-up of 36 months (range 26-62 months), there was neither recurrence nor death from oncocytoma. Accordingly, the disease-specific survival was 100%. Renal oncocytoma has a benign clinical course with excellent long-term outcomes. In our series, it happened mostly in females and is more frequently symptomatic. Although radical nephrectomy is the usual treatment, a conservative approach should be considered whenever there are signs of clinical and radiological presumptions.