We presented a polypoid leiomyoma with bizarre nuclei having atypical endometrial stromal cells adjacent to the leiomyoma. Although atypical stromal cells of the female genital tract have been described, to our knowledge, no lesion identical to ours has been reported thus far. These atypical cells may be mistaken for malignant cells on histologic examination, especially in small endometrial samples. To differentiate these kinds of atypical-featured lesions from sarcoma is important, especially in curettage materials. The etiology and precise nature of multinucleated giant cells and atypical stromal cells in the endometrium are unclear. To prevent radical surgery, pathologists must be familiar with these atypical cells in the female genital tract.