Multilocular cystic renal cell carcinoma in lower pole moiety of a duplex kidney.

Multilocular cystic renal cell carcinoma (MCRCC) is an uncommon low-grade renal cell carcinoma with unique morphologic features. The 2004 World Health Organization classification of kidney tumors categorized MCRCC as a separate entity. The authors report the case of a 48-year-old man whose MCRCC originated from the lower portion of the duplex kidney (DK). Because the oncological outcome of MCRCC is favorable, regardless of tumor size and stage, patients with MCRCC might benefit from nephron-sparing surgery. It is important to distinguish larger MCRCCs from other renal cell carcinomas, especially when comorbid with DK, because the characteristic anatomy of DK warrants the nephron-sparing surgery. To the authors' knowledge, MCRCC in DK has not been reported previously in the English literature.