neurosecretory granules in small cell invasive carcinoma of the urinary bladder a 69yearold man showed symptoms of urinary bladder irritability and hematuria cystoscopy and radiographic studies revealed a tumor within a bladder diverticulum the tumor shared histologic and ultrastructural features with oat cell carcinoma of the lung including the presence of small numbers of neurosecretory type granules in spite of conservative surgical treatment there has been no evidence of recurrent or metastatic tumor over 14 months of followup hypophosphatemia was present preoperatively but resolved spontaneously after tumor resection in regard to histogenesis a metaplastic origin is favored this appears to be the first reported case of a neoplasm of kultschitzkytype cells arising in the urinary bladder