Adenocarcinoma of the urinary bladder.

Adenocarcinoma is an uncommon malignancy in the urinary bladder which may arise primarily in the bladder as well as secondarily from a number of other organs. Our aim is to provide updated information on primary and secondary bladder adenocarcinomas, with focus on pathologic features, differential diagnosis, and clinical relevance. Primary bladder adenocarcinoma exhibits several different growth patterns, including enteric, mucinous, signet-ring cell, not otherwise specified, and mixed patterns. Urachal adenocarcinoma demonstrates similar histologic features but it can be distinguished from bladder adenocarcinoma on careful pathologic examination. Secondary bladder adenocarcinomas may arise from the colorectum, prostate, endometrium, cervix and other sites. Immunohistochemical study is valuable in identifying the origin of secondary adenocarcinomas. Noninvasive neoplastic glandular lesions, adenocarcinoma in situ and villous adenoma, are frequently associated with bladder adenocarcinoma. It is also important to differentiate bladder adenocarcinoma from a number of nonneoplastic lesions in the bladder. Primary bladder adenocarcinoma has a poor prognosis largely because it is usually diagnosed at an advanced stage. Urachal adenocarcinoma shares similar histologic features with bladder adenocarcinoma, but it has a more favorable prognosis than bladder adenocarcinoma, partly due to the relative young age of patients with urachal adenocarcinoma.