Sarcomatoid carcinoma with a predominant basaloid squamous carcinoma component: the first report of an unusual biphasic tumor of the ureter.

Malignant tumors of the ureter that display biphasic patterns are very rare; they include carcinosarcomas, sarcomatoid carcinomas and carcinomas with pseudosarcomatous stroma. Although the distinction between carcinosarcomas and sarcomatoid carcinomas has been extensively discussed in the past, the recent World Health Organization classification of urinary tract tumors (2004) does not distinguish the two lesions and use the term sarcomatoid carcinoma to represent these biphasic tumors. The epithelial components of previously reported ureteral biphasic tumors comprise transitional cell carcinoma, squamous cell carcinoma, carcinoma in situ, small cell carcinoma and adenocarcinoma. In this paper, we report the first case of sarcomatoid carcinoma of the ureter with a predominant basaloid squamous carcinoma component. A 63-year-old man who had developed asymptomatic gross hematuria was diagnosed with a right ureteral tumor and underwent a right nephroureterectomy. Macroscopic examination of the excised tumor revealed a polypoid mass. Histopathologic examination exposed a tumor with malignant epithelial and sarcomatous components. The malignant epithelial component was predominantly composed of basaloid squamous carcinoma, and the sarcomatous component was mostly composed of undifferentiated spindle cells. A small focus of a chondrosarcomatous component was present. There were also transitional zones between the two components. In addition, the spindle cells of the sarcomatous component were partially positive for cytokeratin 7. We believe that the findings of this case study will increase the morphological diversity used for diagnosing malignant tumors of the ureter.