[A case of mucinous tubular and spindle cell carcinoma of the kidney].

Mucinous tubular and spindle cell carcinoma (MTSCC) is a distinct entity in the World Health Organization classification of kidney tumors since 2004. Herein, we report a case of a patient with MTSCC of the kidney. A 48-year-man visited our hospital with a chief complaint of occult blood in his urine, confirmed by urine occult blood reaction. Computed tomography revealed a solid tumor in the right kidney. The tumor was 40×38 mm in length and was slightly enhanced (cT1aN0M0). Therefore, we performed radical nephrectomy. On analysis of the resected specimen, we found that the number of comparatively small malignant cells had increased markedly, forming branched tubular cuboidal cells. Further more, positive results were obtained on staining the stroma with both PAS and alcian blue stains characteristic of papillary renal cell carcinoma ; however, extracellular mucinous material was found to be depleted. Therefore, we needed to differentiate between papillary renal cell carcinoma and MTSCC. Finally, on the basis of the immunohistochemical staining results-vimentin (＋), CK34βE12 (-), and CD10 (-)-MTSCC was confirmed.