Answer: Secondary bladder involvement by recurrent colonic adenocarcinoma

Histology: The glandular neoplasm show morphologic features suggestive of intestinal differentiation including the presence of “dirty’ necrosis. Better differentiated area acquire a villous architecture that may be falsely interpreted, in the absence of an adequate clinical history, as a background intestinal metaplasia/dysplasia leading to misinterpretation of the lesion as a primary bladder adenocarcinoma with intestinal features.

Discussion: Urinary bladder involvement by a secondary tumor either as a metastasis or by direct extension, occur most commonly from colorectal (33%), prostatic (12%) and cervical (11%) sites. Less common sources include breast, stomach, lung and melanoma primaries.

Spread from colonic or rectal primary could represent a diagnostic challenge in Bladder transurethral resection (TUR) samples. In fact, such secondary involvement is a more common occurrence than a primary adenocarcinoma of the bladder. Differentiating a CRCa spread from “intestinal type” adenocarcinoma primary adenocarcinoma of bladder can not be made with certainty. The presence of a background of urothelial intestinal metaplasia with associated glandular dysplasia may favor a primary origin, however, one should be aware of the possibility of colonization of the bladder urothelial mucosa by a secondary well differentiated CRCa mimicking intestinal metaplasia/dysplasia background. In general, a recommendation to rule out spread from a colorectal primary should be forwarded in order to avoid a potentially unjustifiable radical cystectomy procedure. Immunostains including CDX2, B-catenin, villin and CK7/CK20 have been shown to be helpful by some authors. However, some degree of overlap in staining patterns among primary “enteric type” bladder adenocarcinoma and secondary colorectal adenocarcinoma can still exist on an individual case basis.

Reference(s):
– Wang HL, Lu DW, Yerian LM, et al. Immunohistochemical distinction between primary adenocarcinoma of the bladder and secondary colorectal adenocarcinoma. Am J Surg Pathol 2001;25:1380-7.
– Raspollini MR, Nesi G, Baroni G, Girardi LR, Taddei GL. Immunohistochemistry in the differential diagnosis between primary and secondary intestinal adenocarcinoma of the urinary bladder. Appl Immunohistochem Mol Morphol 2005;13:358-62.
– Silver SA, Epstein JI. Adenocarcinoma of the colon simulating primary urinary bladder neoplasia. A report of nine cases. Am J Surg Pathol 1993;17:171-8.