There are 2 general types of adenocarcinomas in the bladder:
Those arising from the urachus (urachal adenocarcinoma, ~1/3), and those arising from the bladder itself (~2/3) (image A).
Primary adenocarcinoma of the bladder overall is rare, and accounts for only 1% of bladder carcinomas.
Suggested to arise from intestinal metaplasia of the urothelium.
Nonfunctioning bladder, chronic irritation, obstruction, exstrophy are risks.
Tumor should be purely gland forming (distinguish from urothelial carcinoma with glandular differentiation).
Several morphologic patterns such as enteric(looks like colorectal adenocarcinoma!) (image B), (image C), & (image D), adenocarcinoma not otherwise specified, mucinous, signet ring cell, hepatoid or mixed (2 or >patterns).
Signet ring cell type may diffusely invade the bladder wall (similar to linitis-plastica in gastric carcinoma).
Should always include metastasis or extension from an intestinal adenocarcinoma, before making the diagnosis.
Immunohistochemistry: expresses enteric marker CDX2, but unlike colorectal adenocarcinoma has more CK7+ and is nuclear β-catenin-.
Staging is the same for urothelial carcinoma.
Prognosis is poor with 5-year survival rate of 18-47%, and high proportion presents with higher stage including up to 40% with metastasis at the time of diagnosis.