A case of sarcomatoid carcinoma of the bladder is reported herein. Immunohistochemical staining with human pancytokeratin antibody was negative, while vimentin staining was strongly positive, suggesting a diagnosis of sarcoma of the bladder. Further immunohistochemical analysis revealed positivity for AE1/AE3 cytokeratins, permitting a correct diagnosis of sarcomatoid carcinoma of the bladder. It can be difficult to distinguish between sarcomatoid carcinoma, undifferentiated carcinoma and sarcoma, particularly if the biopsy specimens are of small size. In rare cases, sarcomatoid tumors may express epithelial markers different from those revealed by human pancytokeratin staining.