Abstract: PD66-02
Sources of Funding: none

Introduction

Chromophobe and oncocytoma represent two distinct renal tumor subtypes stemming from a similar line of differentiation. Apparent overlap in morphology can make definitive diagnosis difficult. A variety of histologic descriptions for these tumors - oncocytic neoplasm, hybrid oncocytic, and unclassified renal cell carcinoma (RCC) with oncocytic features - create both treatment and surveillance dilemmas for the practicing urologist. Are these descriptive nuances important? We hypothesized that recurrence and survival of patients whose tumors exhibit predominantly oncocytic features would be similar, regardless of pathologic variation, and would compare favorably to those tumors defined as pure chromophobe RCC.

Methods

Using data from three high volume institutions, we grouped tumors into four categories: pure oncocytoma, oncocytic neoplasms, renal cell carcinoma unclassified with predominantly oncocytic features, and pure chromophobe tumors. Tumor characteristics and oncologic outcomes were then collected.

Results

A total of 367 patients were identified. Tumor characteristics, demographic information, and oncologic outcomes are reported below (table 1). 168 radical and 199 partial nephrectomies were performed. Median follow-up time for the overall cohort was 25 months (IQR 6 - 65 months). Deaths were rare, and no patients developed recurrence, metastasis, or was felt to have died as a result of their tumor in the non chromophobe groups. In the chromophobe cohort, 4 patients (3%) experienced disease recurrence. A total of 6 patients (4%) died during follow up and 4 patients (3%) were felt to have died of disease. In chromophobe patients who developed disease recurrence, tumors were predominantly larger (mean 12.3cm) with sarcomatoid differentiation in 50%.

Conclusions

Variant tumors with oncocytic features behave more like oncocytoma than renal cell carcinoma. "Atypical features", when present, are permissible as long as the gross appearance remains compatible with oncocytoma. These tumors require little to no post-operative surveillance as opposed to chromophobe RCC, where follow up is warranted. Whether surgery can be obviated altogether when these tumors are diagnosed on preoperative renal mass biopsy requires further evaluation.

Funding

none