Vulvovaginal mesenchymal lesions

Abstract

The wide variety of mesenchymal lesions that involve the vulvovaginal region can result in diagnostic difficulties for pathologists, in part because of their relative rarity but also because of overlapping morphological features. They can be divided into those lesions which are specific to or characteristic of this site and those which can occur at any site with no predilection for the vulvovaginal region. Many of the site-specific or characteristic lesions are thought to arise from the specialized subepithelial stroma of the lower female genital tract that extends from the cervix to the vulva; the stromal cells of this region are hormone responsive and exhibit positive immunohistochemical staining with estrogen receptor (ER) and progesterone receptor (PR). As a consequence, most of the site-specific mesenchymal lesions are positive with ER and PR. Immunoreactivity with both desmin and CD34 is also common; this constitutes an unusual immunophenotype since mesenchymal lesions at other sites are uncommonly positive with both markers. The best known of the site-specific lesions is aggressive angiomyxoma, an infiltrative neoplasm with a marked propensity for local recurrence following excision. Recent developments with regard to aggressive angiomyxoma include the description of occasional metastasizing cases, the potential value of gonadotropin-releasing hormone agonists in management and the emergence of HMGA2 as a valuable diagnostic marker. Most of the other site-specific mesenchymal lesions are well circumscribed and exhibit little tendency for local recurrence. These include angiomyofibroblastoma, fibroepithelial stromal polyp, superficial myofibroblastoma of the lower female genital tract, and cellular angiofibroma. Smooth muscle tumors also occur in this region and are more likely than their uterine counterparts to have an epithelioid or myxoid appearance. Vulvovaginal smooth muscle neoplasms exhibit a propensity for local recurrence and the morphological features which predict malignant behavior differ from uterine smooth muscle neoplasms. Relatively, recently described mesenchymal lesions in the vulvovaginal region include massive vulval edema, prepubertal vulval fibroma, and reactive fibroblastic and myofibroblastic proliferation of the vulva (cyclist's nodule). Gastrointestinal stromal tumors have been described as primary neoplasms in the rectovaginal septum and vagina (termed extragastrointestinal stromal tumors). A wide range of other mesenchymal lesions potentially occur in this region, and it is stressed that when dealing with a vulvovaginal mesenchymal lesion, as well as considering the site-specific lesions, pathologists should consider a wide range of diagnoses since many mesenchymal lesions potentially occur in this region.