Fine needle aspiration biopsy of renal mucinous tubular and spindle cell carcinoma: report of two cases.

Mucinous tubular and spindle cell carcinoma (MTSCC) is a rare renal tumor. Here we report two cases of MTSCC which were initially evaluated by fine needle aspiration biopsy (FNAB) and followed by surgical resection of the tumors. The cytomorphologic features of MTSCC were characterized by aggregates of relatively uniform, predominantly oval to spindle cells intermixed with abundant metachromatic myxoid matrix. Only rare epithelioid tumor cells with vacuolated cytoplasm were present. Immunohistochemically, the tumor cells were positive for CK7, CK19, CD10, vimentin, E-cadherin, alpha-methyl CoA racemase, and negative for CK903 and CK20. EMA and carbonic anhydrase IX immunoreactivity was seen in one of the two cases. Multiple chromosomal losses involving chromosomes 1, 2, 17 and likely chromosome 7 were revealed by fluorescence in situ hybridization (FISH). These cytomorphologic, immunophenotypic, and cytogenetic features were helpful for including this entity in the differential diagnosis of renal cell carcinomas. (c) 2009 Wiley-Liss, Inc.