Vulvar Paget disease of urothelial origin: a report of three cases and a proposed classification of vulvar Paget disease.

Extramammary Paget disease is generally considered a distinct entity that can involve the genital tract skin and may be associated with underlying adenocarcinoma. Evidence is presented that vulvar Paget disease represents a heterogeneous group of epithelial neoplasms that can be similar both clinically and histopathologically. Three cases of vulvar Paget-like disease that were manifestations of urothelial carcinoma are investigated. Vulvar Paget disease can be classified based on the origin of the neoplastic Paget cells as either primary (of cutaneous origin) or secondary (of noncutaneous origin). Each classification has 3 subtypes: primary, intraepithelial cutaneous Paget disease of the usual type; intraepithelial cutaneous Paget disease with invasion, and intraepithelial cutaneous Paget disease as a manifestation of underlying skin appendage adenocarcinoma; secondary, Paget disease of anorectal origin, Paget disease of urothelial origin, and Paget disease of other origin. This subclassification is based on a review of the literature and the current study of 3 patients with Paget-like disease of urothelial neoplastic origin. The 3 subtypes of vulvar Paget disease studied here can present similarly as eczematoid skin or vulvar mucosal lesions and may appear similar on routine hematoxylin and eosin-stained slides. Immunohistochemical studies can be used to help differentiate them. The distinction between these 3 types of Paget-like lesions is essential in that the specific diagnosis has a significant influence on current treatment. The difference in surgical approach to the subtypes of vulvar Paget disease justifies classifying them into distinct lesions to avoid potential confusion and unnecessary surgery.