[1024] Utility of Uroplakin and PAX-2 Immunohistochemistry in the Diagnosis of Primary Adenocarcinoma of the Urinary Bladder

H Ye, X Wu, DE Hansel, J Melamed, JI Epstein. New York University School of Medicine, New York; Cleveland Clinic, Cleveland; The Johns Hopkins Hospital, Baltimore

Background: In cases of adenocarcinoma involving the bladder without an in situ component, it is important to rule out spread from an unknown primary. Uroplakin (UP) is a lineage specific marker for urothelial carcinoma, but has not been studied in bladder adenocarcinomas. In the bladder, PAX2 is expressed in nephrogenic adenoma and clear cell adenocarcinoma. PAX2 is also expressed in cancers from the fallopian tubes, endometrium, endocervix, and a small fraction of colonic adenocarcinomas.
Design: Two tissue microarrays (TMAs) were previously constructed from representative regions of tissue from 48 primary adenocarcinomas of the bladder including 10 signet ring cell carcinomas and 1 urachal adenocarcinoma. The TMAs also included 3 prostatic urethral adenocarcinomas, 2 bladder villous adenomas, 3 cases of benign intestinal metaplasia, and benign and malignant tissues from various organs. TMA sections were stained with anti-uroplakin (a polyclonal pan-UP antibody recognizing UPIII, UPIb, and UPII) and a monoclonal anti-PAX2 antibody.
Results: Only one of the 37 cases of enteric-type bladder adenocarcinomas stained positive for uroplakin. Of the 10 signet ring cell carcinomas, 6 cases had focal to patchy immunoreactivity for anti-UP. UP expression was not detected in prostatic urethral adenocarcinoma, villous adenoma, or intestinal metaplasia. Of the 48 primary adenocarcinomas of the bladder, only 1 enteric-type adenocarcinoma stained weakly positive for anti-PAX2. The patient of the PAX2 positive case had a remote history of hysterectomy, therefore a uterine primary could not be completely ruled out. One of the 3 cases of prostatic urethral adenocarcinoma showed focal PAX2 staining. PAX2 expression was not detected in bladder villous adenoma or in intestinal metaplasia.
Conclusions: Uroplakin immunostaining has no diagnostic value in differentiating enteric-type adenocarcinoma of the bladder from secondary spread from other tumors. Uroplakin immunopositivity may be useful in establishing a diagnosis of primary signet ring cell carcinoma of the bladder. PAX2 immunopositivity rules out a bladder primary adenocarcinoma. Considerations in such cases should be given for primary clear cell adenocarcinoma of bladder, secondary involvement by an oviduct adenocarcinoma, and to a lesser degree, a colorectal primary.
Category: Genitourinary (including renal tumors)

Tuesday, March 23, 2010 1:00 PM

Poster Session IV # 87, Tuesday Afternoon


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