Atypical leiomyoma also known as bizarre or symplastic leiomyoma is a smooth muscle tumor of the uterus that contains a variety of giant smooth muscle cells with multiple pleomorfic nuclei and clumping chromatin. It’s biological potential is determinated by mitotic index and tumor necroses, considering as malignant those with 10 or more MF/ 10HPF. Considering a new case of atypical leiomyoma of the uterus and revision of the desease, clinical and pathological aspects are described.

Keywords: 1. Atypical leiomyoma;
2. Giant smooth muscle cells;
3. Clumping chromatin;
4. Mitotic index;
5. Tumor necroses.