Benign Vaginal Mesenchymoma Showing Mature Skeletal Muscle,Smooth Muscle,and Fatty Differentiation

A 28-year-old woman presented with a firm mass in the rectovaginal septum, noted incidentally during vaginal delivery of a term neonate. The mass was composed of three rounded, semiconfluent, submucosal nodules that “shelled out” surgically. The main histologic features were a hyalinized and myxoid background stroma showing variable vascular patterns of both thick and thin-walled vessels and occasional spindle cells. Embedded in this stroma were varying numbers of single or small groups of mature, mitotically inactive, rhabdomyocytes, smooth muscle cells, and adipocytes. The rhabdomyocytes tended to be arranged radially in focal aggregates and were found in only one of the three tumor nodules, while the smooth muscle and fatty elements were more random and widespread in distribution. We have not encountered such a lesion in the literature and have designated it as a benign mesenchymoma of the vagina.