Oat cell carcinoma of the urinary tract. An immunohistochemical and electron microscopic study

Four oat cell carcinomas of the urinary tract (three of the bladder and one of the ureteropelvic junction) were studied using immunohistochemical and electron microscopic methods to evaluate the possible histogenesis of these tumors. Ultrastructurally, the oat cell component of the tumors had neurosecretory-type granules and positive immunoreaction for neuron-specific enolase, indicating the endocrine nature of the tumors. Three tumors were mixed with a non-oat cell component: adenocarcinoma and/or transitional carcinoma or carcinoid tumor. There are no previous reports of mixed oat cell and adenocarcinoma or carcinoid tumor of the urinary tract. This report is also the first of an oat cell carcinoma originating in the pelvic ureteric junction.