Small cell carcinoma arising from the outer urethral orifice: A case report examined by histologic, ultrastructural and immunohistochemical methods

A case of small cell carcinoma arising In the outer urethral orifice is presented. The resected tumor showed a proliferation of small round or fusiform neoplastic cells in the submucosa. Tumor cells were arranged in sheets or a trabecular manner and possessed markedly hyper‐chromatic nuclei with a high N: C ratlo, closely resembling small cell carcinoma of the lung. Characteristically, pagetoid lntraepithellal spreading could be identified. However, there was no evidence of in sku transitional cell carcinoma and adene or squamous cell carcinoma components anywhere. Ultrastructurally, each tumor cell contained only a few membrane‐bound cored granules measuring 60–100 nm, which were compatible with neurosecretory granules, and desmosomellke Intercellular attachments, but lacked aggregated microfilaments. By immunohistochemical examination, tumor cells were positive for eplthelial markers, such as cytokeratln and epithellal membrane antlgen, and neuron specific enolase, but negative for any other neuro‐endocrine markers. Extensive systemic examinatlon falled to show the primary site to be other than the outer urethral oritlce. These findings lndicate that the current tumor is a small cell carclnoma with neume‐ndocrine differentiation arising from the outer urethral orifice.