The possibility that a fibroid may actually be a smooth muscle tumor of uncertain malignant potential or a leiomyosarcoma often dictates the clinical management of rapidly growing fibroids. This article provides a clinicopathologic background regarding uterine leiomyosarcomas and answers common questions that obstetricians and gynecologists have about the management of rapidly growing fibroids and leiomyosarcoma. The clinician must be aware that the infrequent occurrence of uterine leiomyosarcomas makes it difficult to establish absolutely firm recommendations for the diagnosis and management of this disease, particularly with regard to fertility preservation. Nevertheless, this article addresses major issues that a clinician might face in the evaluation of a smooth muscle tumor of the uterus that clinically may be malignant.