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 areas 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.

The table summarizes the findings of the studies listed below(see references) regarding immunostains utility in differentiating primary bladder adenocarcinoma, intestinal type from secondary involvement of bladder by a spread from a colorectal primary.

Discussion: The overwhelming majority of genitourinary tumors are primary epithelial neoplasms with only a minority representing a spread from a non-genitourinary site or other genitourologic primary site. 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 samples. In fact, such secondary involvement is a more common occurrence than a primary adenocarcinoma of the bladder. Differentiating a colorectal carcinoma spread from “intestinal type” adenocarcinoma primary adenocarcinoma of bladder cannot 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 colorectal carcinoma mimicking a vesical iintestinal 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 still exist on an individual case basis.

Among other rare sources of primary tumors metastasizing to bladder, mammary carcinoma deserves a cautionary note. The possibility of a breast metastasis should be raised when presented with an epithelial infiltration in the form of cords or individual, at times plasmacytoid to signet ring shaped, cells involving the lamia propria without associated overlying papillary urothelial proliferation or “flat’ CIS. In such cases, the differential diagnosis should also include a rare variant of urothelial carcinoma, namely plasmacytoid/signet ring variant. Obtaining a proper clinical history and the use of immunohistochemistry (ER, PR, Gross cystic disease fluid protein “GCDFP”, uroplakin and thrombomodulin) will help reach a proper diagnosis.

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.
– Bates AW, Baithun SI. Secondary neoplasms of the bladder are histological mimics of nontransitional cell primary tumours: clinicopathological and histological features of 282 cases. Histopathology 2000;36:32-40.
– Jacobs LB, Brooks JD, Epstein JI. Differentiation of colonic metaplasia from adenocarcinoma of urinary bladder. Hum Pathol 1997;28:1152-7.
– Suh N, Yang XJ, Tretiakova MS, Humphrey PA, Wang HL. Value of CDX2, villin,
and alpha-methylacyl coenzyme A racemase immunostains in the distinction
between primary adenocarcinoma of the bladder and secondary colorectal
adenocarcinoma.Mod Pathol. 2005;18(9):1217-22. PubMed PMID:
15803184.