A reassessment of uterine neoplasms originally diagnosed as leiomyosarcomas

Twenty-eight uterine tumors originally diagnosed as leiomyosarcomas were histologically reclassified without prior knowledge of follow-up or clinical data. Thirteen (46%) neoplasms were reinterpreted as cellular or pleomorphic leiomyomas. They had sparse mitotic activity with three or fewer mitotic figures per 10 high power microscopic fields (MF/10 HPF). None recurred or metastasized, and all patients were alive from 6.3 to 23 years after operation (median of 14.2 years). In 15 cases the diagnosis of leiomyosarcoma (LMS) was confirmed. All showed hypercellularity, nuclear atypism and high mitotic activity. Mitosis counts ranged from 6 to more than 50 MF/10 HPF with 93% of LMS having at least 15 MF/10 HPF. These patients all died of LMS after post-operative intervals of 3 months to 7.5 years (median survival of 13 months). No consistent correlation was found between length of survival and the patient's menopausal status or histologic grade of LMS. The degree of mitotic activity is the single most reliable diagnostic criterion of malignant potential, albeit not the only one. Surgery alone is ineffective treatment for LMS and combination therapy with radiation therapy and/or chemotherapy should be considered.