Primary signet ring cell carcinoma of bladder exemplifying vesical epithelial multipotentiality.

The eighth reported case of primary signet ring cell carcinoma of the urinary bladder is described clinically and pathologically. It is unusual because of complete replacement of the transitional epithelium by squamous and glandular metaplasia. The latter was particularly striking, demonstrating "normal" colonic mucosa, cystitis glandularis, well-differentiated adenocarcinoma, poorly differentiated adenocarcinoma, and the rare signet ring cell carcinoma variant. The possible origin of such changes is discussed.