Comparative analysis of histopathological subtypes of renal cell carcinoma in the Middle East compared to other world regions

Introduction: Renal cell carcinoma (RCC) has various histopathological tumor subtypes which have a significant implication on the oncological outcome of these patients. We aimed to evaluate the distribution of RCC subtypes presenting at a tertiary care center in the Middle East, in comparison to the distribution reported in different geographic areas worldwide. Methods: A retrospective chart review was conducted on all patients who underwent partial or radical nephrectomy for RCC at the American University of Beirut Medical Center between January 2012 and January 2018. Data on histologic subtypes were compiled and compared to representative series from different continents. Results: One hundred and seventy-nine patients with RCC were identified, of whom 122 (68.2%) were classified as clear cell, 30 (16.8%) as papillary, 17 (9.5%) as chromophobe, and 10 (5.6%) as unclassified. When compared to other regions of the world, this Middle Eastern series demonstrated a higher prevalence of the chromophobe subtype compared to Western populations (9.5% in the Middle East vs. 5.3% in the US and 3.1% in Europe) and a lower prevalence of clear cell subtype (68.2% in the Middle East vs. 78.7% in the US and 85.8% in Europe). Conversely, there was a higher prevalence of papillary RCC in the Middle East (16.8%) compared to North America (13.1%, 95% confidence interval [CI]: 12.7–13.6), Europe (11.1%, 95% CI: 10.0–12.1), and Australia (10.2%). The prevalence of chromophobe and clear cell RCC in the Middle East was similar to that reported in South America. Conclusions: The distribution of RCC subtypes in this Middle Eastern cohort was significantly different from that reported in the Western hemisphere (Europe and the US) but similar to that reported in South America and Australia. These findings may point to a possible genetic predisposition underlying the global variation in distribution.