Mitotically active leiomyomas of the uterus.

Seventy-three smooth-muscle tumors of the uterus, with five to nine mitotic figures per 10 high-power fields but lacking cytologic atypia, were studied. Pathologic features assessed included necrosis, hemorrhage, vascular intrusion, abnormal mitoses, and the number of mitotic figures. Vascular ingrowth by the tumor was present in 11 neoplasms. Follow-up ranged from 23 months to 15 years, with all patients alive and well at last contact. In 14 patients, myomectomy was the only treatment. Thirteen of these patients demonstrated no subsequent residual or recurrent tumor. One woman developed a persistent or recurrent mitotically active leiomyoma 8 years after myomectomy. We conclude that mitotically active smooth-muscle tumors of the uterus, having five to nine mitoses per 10 high-power fields and no cellular atypia, have a metastatic rate too low to be regarded as sarcomas. Hysterectomy need not automatically follow myomectomy if follow-up is done.