Abstract

Over the past few years, the increasing use of cross‐sectional imaging, including ultrasound and computed tomography imaging, resulted in an increase incidental diagnosis of renal tumors, especially small renal masses (< 4 cm). The knowledge that 30% of these masses may be benign, including oncocytomas led to the investigation for more effective methods of diagnosis in order to avoid overtreatment situations. The authors decided to analyse and compare contrast enhancement patterns of oncocytomas and clear‐cell renal cell carcinoma (ccRCC) to predict histology. Between 2004‐2015 we retrospectively identified 32 patients with either histological confirmation of renal oncocytoma (N = 16) or ccRCC (N = 16) who underwent percutaneous biopsy, total or partial nephrectomy. The relative attenuation of solid renal lesions and normal renal cortex was determined in the unenhanced and nephrographic phase. Statistical comparison was carried out by Mann‐Withney test. The oncocytomas and cc‐RCC average size was 3.7 cm [1.8 to 14] and 3.5 cm [1.9 to 8.4], respectively. The average attenuation in the unenhanced phase was 33 HU and 32 HU, respectively. In nephrographic phase, the average contrast enhancement was 47.5 and 47.4 H, respectively. In nephrographic phase, the attenuation difference between the oncocytomas and normal renal cortex was 43.5 HU and the attenuation difference between the cc‐RCC and normal renal cortex was 59.7 HU. These results were statistically significant (p < 0.05). In the nephrographic phase, URO‐CT reveals that oncocytomas have greater isodensity to the normal renal cortex compared to cc‐RCC. This finding can help us to determine which lesions we should biopsy or not.

Abstract

Renal oncocytoma account for 3 to 7% of primary renal tumors. It is usually diagnosed incidentally and typically has a benign behavior. No currently used imaging techniques can reliably distinguish it from malignant lesions. Similarly, the microscopic diagnosis of oncocytoma remains a challenge. We present a case of an asymptomatic elderly, hypertensive, diabetic and with moderate chronic renal insufficiency, who underwent radical nephrectomy for a solid exophytic lesion of 4.7 cm in the renal pole, detected accidentally. Pathological examination revealed a renal oncocytoma. In this situation, partial nephrectomy would be the preferred surgical treatment, avoiding the long‐term risk of living with a single kidney. The lack of diagnostic tools that reliably differentiate between benign and malignant lesions makes this an important area of study, in order to reduce the number of surgical interventions and the associated morbidity.