Leiomyosarcomas are rare uterine neoplasms that exhibit a highly malignant behavior. More commonly, these tumors arise de novo from the myometrium. A very small percentage is said to develop from a pre-existing leiomyoma. However, the latter condition of a malignant transformation is unusual. Only a handful of cases have been reported in literature. Perhaps due to its rarity, some gynecologists and pathologists do not even believe of its existence. Presented herein are two cases of leiomyosarcomas, which have, in all probability, arisen from a leiomyoma which underwent a sarcomatous change. (Author)