Combined small and transitional cell carcinoma of the urinary bladder with CA19-9 production.

It is well known that extrapulmonary small cell carcinoma, which exhibits morphological features similar to those observed in the lung, occurs in various organs. Clinically, most cases manifest aggressive biological behavior. A case of small cell carcinoma of the urinary bladder producing a high level of serum carbohydrate antigen (CA) 19-9, in which expression was confirmed in cancer cells of small as well as transitional cell carcinoma in the same tumor mass by immunostaining is reported. This paper documents combined small and transitional cell carcinoma of the urinary bladder with CA19-9 production, although it has already been reported that adenocarcinoma or transitional cell carcinoma in various organs frequently expresses CA19-9. Observations suggest that the histogenesis of some cases of combined small and transitional cell carcinoma in the urinary bladder may be the same, as both can produce CA19-9.