Primary mucinous adenocarcinoma of the bladder with signet-ring cells: case report.

CONTEXT: Primary adenocarcinomas of the bladder are uncommon and usually occur by contiguity with or hematogenic dissemination of other adenocarcinomas such as colorectal, prostate and gynecological tract carcinomas. Mucinous and signet-ring cell histological patterns are even rarer and it is often difficult to morphologically distinguish them from metastatic colorectal adenocarcinoma. CASE REPORT: We present and discuss a rare case of primary mucinous adenocarcinoma of the bladder with signet-ring cells in a 57-year-old male patient. Other primary sites for the tumor had been excluded and, in the absence of digestive tract tumor and for confirmation that it was a primary bladder tumor, an immunohistochemistry study was performed.