Mesenchymal tumors of the lower reproductive tract of women are poorly understood at the molecular level as a result in part of the lack of relevant animal models. The present study describes a novel model of gynecological smooth muscle tumors in which these neoplasms arise in Eker rats as part of a familial cancer syndrome. The tumors develop as a result of a germline mutation in the tuberous sclerosis 2 (TSC2) gene, and predisposition to tumor development is inherited in an autosomal dominant fashion. Uterine and/or cervical tumors arise spontaneously as single or multicentric neoplasms and increase in incidence with increasing age. The tumors were classified into three phenotypic variants of leiomyoma/leiomyosarcoma and into stromal cervicovaginal tumors on the basis of cytological and histological features and immunostaining patterns for smooth muscle actin and desmin. Tumors histologically identical to the typical human myometrial leiomyoma arose, as did a subset of atypical leiomyomas having an epithelioid phenotype. Eker rats were found to develop both benign and malignant smooth muscle tumors. The high spontaneous incidence of smooth muscle tumors of uterus and cervix in this rodent model provides a unique opportunity to study the molecular mechanisms underlying the development of these clinically important gynecological neoplasms.