[Histological diagnosis and clinical features in borderline smooth muscle tumors of the uterus].

Between leiomyoma and leiomyosarcoma there exists a series of borderline smooth muscle tumors of the uterus, including cellular, bizarre, mitotically active, atypical and uncertain malignant potential leiomyomas. A histological criterion was presented in this study for diagnosis of smooth muscle tumors of the uterus. Forty-two cases originally diagnosed as uterine cellular leiomyomas were re-examined histologically, analyzed clinically and followed up. The results showed that among the 42 cases, there were 5 cases of cellular leiomyoma, 1 case of bizarre leiomyoma, 7 cases of atypical leiomyoma, 2 cases of tumors of uncertain malignant potential, 1 case of leiomyosarcoma and 26 cases of usual leiomyoma. The histological criteria of dense cellularity, cell atypia and nuclear mitosis showed a close correlation, but did not vary at different phases of menstrual cycle. Clinical features of borderline tumors were similar to those of usual leiomyomas, and their prognosis was also good. It is suggested that diagnosis of borderline smooth muscle tumors of the uterus should be made on the basis of three histological characteristics, including cellular density, cell atypia and nuclear mitotic figures. Management of the borderline cases seems to be the same as that of usual leiomyoma, but a further study may be necessary.