Answer: Cystitis glandularis, intestinal type

Histology: The lesion consists of numerous glands lined by columnar cells, many of which have the appearance of goblet cells. The nuclei are uniform, basally situated and lack overt atypical features. Mitotic figures are difficult to find. The stroma surrounding the glands is myxoid and mucinous. In areas, the urothelium has been replaced by squamous metaplasia.

Discussion: The pattern seen in this case does not resemble any of the morphology seen within adenocarcinoma of the prostate. One cannot distinguish morphologically between infiltrating adenocarcinoma from the colon versus adenocarcinoma of the bladder. Consequently, the differential diagnosis in this case rests between infiltrating adenocarcinoma whether from bladder of colon versus florid intestinal type cystitis glandularis. Infiltrating adenocarcinomas of the bladder are entirely analogous with the full spectrum adenocarcinomas seen within the gastrointestinal tract. This includes enteric, signet ring cell, and colloid patterns. With rare exception, adenocarcinomas of the bladder have overt cytlogic atypia with a desmoplastic stromal reaction where it is easy to identify the glands as malignant. In contrast, glands within the current specimen are lined by cytologically bland epithelium and it is only the pattern of crowded glands surrounded by mucin extravasation that architecturally resembles carcinoma. However, cystitis glandularis of the intestinal type may show mucinous extravasation and rarely even involves the muscularis propria. Consequently, all of the findings in the current case are classic for cystitis glandularis, intestinal type with no features worrisome for adenocarcinoma. It is critical to recognize that cystitis glandularis, intestinal type may on occasion make a mass lesion that clinically will be strongly suspicious for a neoplasm. Despite the reservations raised by the urologists, it is critical to reassure them that this lesion is benign. On rare occasions, one may see adenomatous foci within cystitis glandularis, intestinal type and in those cases it is recommended that complete but conservative excision be performed to rule out a very rare co-existing infiltrating adenocarcinoma.