Squamous carcinoma of bladder with pseudosarcomatous stroma

A polypoid squamous cell carcinoma with pseudosarcomatous stroma of the urinary bladder was studied electron microscopically. The epithelial component was a typical squamous carcinoma that consisted of cells with abundant bundles of tonofilaments that converged toward well-developed desmosomes; keratohyalin granules were also seen. The stroma consisted of fusiform cells with dilated rough endoplasmic-reticulum cisternae and irregular cytoplasmic projections that were suggestive of active fibroblasts. No structures suggestive of an epithelial origin or of advanced mesenchymal differentiation were recognized. These observations are consistent with the notion that the pseudosarcomatous stroma represents a reactive process that is probably related to the growth of the epithelial neoplasm. Given the differences in behavior and prognosis between carcinomas with pseudosarcomatous stroma and true carcinosarcomas, efforts at separation of these entities are warranted.