Collecting duct carcinoma: a rare renal tumor.

The most common primary malignant renal tumor is renal cell carcinoma (RCC), which accounts for 3% of all adult malignancies. Bellini duct carcinoma or collecting duct carcinoma is an unusual rare variant of RCC. This histologically distinct tumor is very rare, with less than 100 cases reported in the literature, and accounts for approximately 1% of all malignant renal epithelial tumors. We report two cases of collecting duct carcinoma and highlight the rarity of these tumors and their similarity to RCC.