Mucinous tubular and spindle cell carcinoma of the kidney with sarcomatoid transformation

Mucinous tubular and spindle cell carcinoma (MTSCC) of the kidney is a recently described entity in the World Health Organization (WHO) 2004 classification and has a relatively indolent behavior. Sarcomatoid differentiation has been well documented in most histologic variants of renal cell carcinoma and its presence is known to have a worse prognosis. Its occurrence in an otherwise benign MTSCC is extremely rare. Here,we report a unique case of MTSCC in a 64-year-old patient with multiple areas of high-grade spindle cells and large areas of necrosis in it. The patient had a rapidly fatal clinical outcome.