ADENOCARCINOMA OF THE URACHUS AND BLADDER EXPRESSES A UNIQUE COLONIC EPITHELIAL EPITOPE - AN IMMUNOHISTOCHEMICAL STUDY

Purpose: Primary adenocarcinoma of the bladder is a rare neoplasm whos e histogenesis is poorly understood. Current data support the concept that adenocarcinoma of the bladder and urachus evolves from zones of i ntestinal metaplasia that become dysplastic and invasive. To address t his hypothesis further we determined the immunoreactivity of benign an d malignant epithelial tissue fi om the bladder and urachus with a mon oclonal antibody that is reactive with colonic epithelium to evaluate the presence of a common reactive epitope. Materials and Methods: The monoclonal antibody 7E(12)H(12) (IgM isotype), developed against a col onic epithelial protein, was used in an immunoperoxidase assay to surv ey formalin fixed, paraffin embedded archival tissue specimens. A tota l of 26 specimens obtained by endoscopic biopsy or extirpative surgery , including benign and malignant bladder and urachal epithelial abnorm alities, was chosen for retrospective evaluation. Results: All adenoca rcinoma reacted positively regardless of the histological variant, dif ferentiation, or bladder or urachal origin. In contrast, transitional cell and squamous cell carcinomas were nonreactive. Also, the pattern of reactivity in tissues that contained benign epithelial proliferatio ns suggested a stepwise transition with no reactivity in normal urothe lium or Brunn's epithelial nests, rare staining of cystitis cystica, a nd uniformly positive reactivity in cystitis glandularis and frank col onic intestinal metaplasia of the bladder and urachus. Conclusions: Th e shared, aberrant; phenotypic expression of a unique colonic epitope in benign epithelial metaplasia, and adenocarcinoma of the bladder and urachus suggests a common underlying pathway toward adenocarcinoma in cystic and urachal adenocarcinoma. The implications for diagnostic pa thology are discussed.