Mucinous tubular and spindle cell carcinoma of kidney without sarcomatoid change showing metastases to liver and retroperitoneal lymph node.

Mucinous tubular and spindle cell carcinoma (MTSCC) is an uncommon, newly recognized tumor that in its classic histological form shows tightly packed, elongated tubules with transition into spindle cell areas and pale mucinous stroma. The current data suggest that the great majority of MTSCCs have a favorable prognosis; however, the follow-up data are limited and the full biologic potential of this tumor remains to be established. There are a few examples of MTSCCs metastatic to lymph nodes and rare cases with sarcomatoid differentiation associated with distant metastases. We report on a case of MTSCC of kidney with concurrent nodal and liver metastases. The metastatic nodules were well circumscribed and showed morphological and immunophenotypic features similar to those of the primary tumor. Extensive sampling revealed no evidence of sarcomatoid morphology. To our knowledge, this is the first case of MTSCC without sarcomatoid differentiation showing parenchymal metastasis.