Renal collision tumor composed of oncocytoma and mucinous tubular and spindle cell carcinoma: case report of an unprecedented entity

Primary renal collision tumors composed of two histologically distinct components are rare with only isolated case reports in the medical literature. Oncocytoma is a benign renal neoplasm, which is thought to originate from distal tubular epithelial cells. Mucinous tubular and spindle cell carcinoma (MTSCC) of kidney is a rare, relatively recently described renal neoplasm that was first included in the 2004 World Health Organization RCC classification as a distinct entity. Current studies suggest the tumor originates from the proximal nephron, although it is still controversial.

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