Primary signet cell adenocarcinoma of bladder.

Primary signet cell cancer of the urinary bladder is a relatively rare entity. Since there is no mucinous epithelium in the bladder, It is proposed that the tumor arises from metaplastic urothelium. Two thirds of the tumours are mucin secreting, in most of which the site of the deposition is either extracellular or intracellular displacing the nucleus to a peripheral crescent, giving the cells a signet ring appearance. The tumours are most often infiltrative and diffusely involving the majority of the bladder akin to its name sake in stomach. It is essential to distinguish this carcinoma from gastrointestinal metastases as different therapeutic strategies are often necessary.