Bladder, Urothelial carcinoma, sarcomatoid variant

Urothelial carcinoma is the most common malignancy of the urinary bladder in western countries. Risk factors for developing urothelial carcinoma include tobacco smoking and exposure to aromatic amines. Urothelial carcinomas are so named because their histogenesis is from the normal urothelial lining of the bladder, and their histologic appearance usually recapitulates this. There are, however, several morphologic variants including sarcomatoid urothelial carcinoma, where the tumour demonstrates areas consisting of a highly cellular proliferation of spindle cells with nuclear atypia and high mitotic rate. They can occasionally also demonstrate the presence of heterologous elements, such as bone and cartilage. In this case, other sections showed areas of traditional urothelial carcinoma in situ, and a previous biopsy showed patchy positive immunohistochemical staining for p63, cytokeratins, and GATA3; supporting the diagnosis of sarcomatoid urothelial carcinoma and not a mesenchymal lesion.