Vulvar Paget's disease. Is immunocytochemistry helpful in assessing the surgical margins? From January 1977 to December 1988, 19 patients with biopsy-proven Paget's disease of the vulva underwent simple or radical vulvectomy at the University of Miami/Jackson Memorial Medical Center. All vulvectomy specimens were evaluated immunocytochemically for the expression of carcinoembryonic antigen (CEA), epithelial membrane antigen (EMA) and low-molecular-weight keratins 8 and 18 (LMK), both in areas containing neoplastic cells and in histologically negative surgical margins. Neoplastic Paget's cells stained positively for CEA in all cases; they were positive for EMA and LMK in 18 and 17 cases, respectively. In all eight cases with underlying in situ or invasive carcinomas, CEA, EMA and LMK were localized in the underlying tumors as well. None of the histologically proven negative margins reacted for CEA, EMA or LMK on immunocytochemistry. CEA appears to be a valuable immunocytochemical marker for extramammary Paget's disease; EMA and LMK are also expressed by the majority of such cases. None of these markers, however, is of added value in identifying Paget's cells in surgical margins if those margins appear negative on routine hematoxylin-and-eosin staining. 