A case of an infiltrating myxopolypoid tumor of the uterus is presented. Histologically, the tumor revealed spindle-shaped cells with mitotic counts ranging between 1-4/hpf, myxoid stroma, and multinucleated giant cells mimicking syncitial giant cells of pregnancy trophoblast. Conventional light microscopic methods failed to establish the histogenesis of the tumor. At the ultrastructural level the tumor showed three main cellular components; myoblasts, myofibroblasts and collagen-producing fibroblasts. On the basis of light microscopic and electron microscopic findings, the tumor was labelled myxoid leiomyosarcoma. This variant of leiomyosarcoma is rare. This is the seventh case reported in the international literature.