Criteria for risk stratification of vulvar and vaginal smooth muscle tumors: a follow-up study with application to leiomyoma variants, smooth muscle tumors of uncertain malignant potential, and leiomyosarcomas.

Data have shown that uterine diagnostic criteria are universal for smooth muscle tumors (SMTs) originating in the ovary, vulva, vagina, broad ligament, and other supportive connective tissue and that uterine criteria outperform site-specific criteria for vulvar and vaginal SMTs. Classic benign and malignant spindled SMTs were well represented in our recent study comparing uterine and site-specific criteria in vulvovaginal SMTs, but leiomyoma variants and smooth muscle tumors of uncertain malignant potential (STUMPs) were relatively few. Therefore, we evaluated additional leiomyoma variants, STUMPs, and leiomyosarcomas from 17 patients (10 vaginal and 7 vulvar). The 10 vaginal tumors (59%) comprised cellular leiomyoma (n = 2), leiomyoma with bizarre nuclei (n = 3), STUMP (n = 1), and leiomyosarcoma (n = 4). The 7 vulvar tumors (41%) comprised leiomyoma with bizarre nuclei (n = 3), STUMP (n = 1), and leiomyosarcoma (n = 3). Follow-up was available for 13 patients (76.5%) ranging from 1 to 97 months (mean: 17.3; median: 7). Follow-up for some patients with leiomyosarcoma was limited (≤4 months for 4 patients). One vaginal STUMP locally recurred after 19 months, and 2 patients diagnosed with leiomyosarcoma developed distant metastases. All remaining patients had either no evidence of disease at last follow-up (10 patients, 58.8%) or their status was unknown (4 patients, 23.5%). Uterine criteria are valid for vulvovaginal leiomyoma variants and STUMPs and more appropriately classified these tumors than site-specific criteria. Our combined findings from the current and previous studies support use of uterine diagnostic thresholds for the entire spectrum of vulvovaginal SMTs.