Leiomyosarcoma is an aggressive soft tissue sarcoma derived from smooth muscle cells typically of uterine, gastrointestinal or soft tissue origin. Sarcomas are malignant tumors arising from mesenchymal cell lines. They comprise a heterogeneous group of cancers, each with unique clinical, histologic, and radiographic characteristics. Soft tissue sarcomas account for 0.7% of malignancies. Sarcomas are generally classified according to the normal cell line that they most closely resemble. Myxoid leiomyosarcoma (mLMS) of the uterus is a rare neoplasm; thus, knowledge of its clinical behavior and morphology remains limited. We therefore reviewed 30 cases initially diagnosed as uterine mLMS to better characterize its clinicopathologic features. Diagnosis was confirmed in 25 subjects (average age 51.5 y), of whom 80% were stage 1 at presentation. The average tumor size was 10.8 cm. An infiltrative tumor border was observed microscopically in 24 cases (96%); the border in 1 case could not be assessed. Fourteen cases (56%) had >10 mitoses per 10 high-power fields, 8 (32%) had between 2 and 10, and 3 cases (12%) had <2 mitoses. Geographic tumor necrosis and moderate to severe nuclear pleomorphism were seen concurrently in 12 cases (48%).