Mucinous tubular and spindle cell carcinoma with aggressive histomorphology—a sarcomatoid variant

Mucinous tubular and spindle cell carcinoma (MTSCC) is a recently described renal epithelial tumor. The bland cytomorphology of the spindled component and low-grade behavior help in its differentiation from sarcomatoid renal carcinoma. Sarcomatoid change has been reported in most histologic variants of renal cell carcinoma apart from MTSCC. Herein we report a case of an MTSCC in a 72-year-old female patient with high-grade spindled areas resembling fibrosarcomatous and undifferentiated pleomorphic sarcoma patterns with metaplastic bone. This index case also demonstrates a high proliferation index and extensive necrosis representing the first documented case of sarcomatoid change in MTSCC.