A rare type of renal tumor - mucinous tubular and spindle cell carcinoma

Mucinous tubular and spindle cell carcinoma (MTSCC) of the kidney, a rare renal cell carcinoma, is a low grade malignant tumor with histogenesis still under debate. We report the case of a 60-years-old female, asymptomatic, with no significant personal or family history, diagnosed on routine ultrasound examination with a unilateral non-homogenous mass in the right kidney. On gross examination the tumor was solid, well circumscribed, and limited to the kidney parenchyma. Microscopically, the tumor was composed from eosinophilic small cuboidal cell arranged in small, tightly packed, parallel tubular structures, myxoid stroma and mucinous areas (PAS and Alcian Blue positive). Therefore, the differential diagnosis between MTSCC and papillary renal cell carcinoma was compulsory. The immunohistochemistry assays confirmed MTSCC as the final diagnosis, based on the intense positive reaction for CK7 and negative reaction for CD10. The present report aimed to highlight the pathological characteristics of this rare subtype of renal cell tumors and to point out the differential diagnosis – particularly with the papillary renal cell carcinoma, given the different prognosis and therapeutic approach of these two entities.