Mucin-Poor Mucinous Tubular And Spindle Cell Renal Cell Carcinoma With Sarcomatoid Transformation And Multiple Metastases: Report Of A Unique Case And Review Of Literature

Mucinous tubular and spindle cell renal cell carcinoma (MTSRCC) is an uncommon, newly recognized tumor that is histologically characterized by small, elongated tubules lined by cuboidal cells and/or cords of spindled cells separated by variable amounts of mucinous/myxoid stroma. Nonclassic morphologic variants and features of MTSRCC have not been well documented and only rarely been studied. Although initially considered to be a low-grade carcinoma with favorable prognosis, MTSRCC demonstrating sarcomatoid transformation with an aggressive behavior has recently been reported. Herein, we present a unique case of MTSRCC with a mucin-poor morphology, extensive high-grade sarcomatoid transformation, multiple metastases and a rapidly fatal clinical course in a 53-year-old man and describe its histomorphologic and immunohistochemical features as well as molecular genetic findings. Our findings further expand both the histological and behavioral spectrums encountered in MTSRCC.