Diagnosis of uterine mesenchymal tumors continues to be challenging because of their nonspecific clinicopathological presentation. Several studies have focused on the underdiagnosis/undertreatment of hidden uterine sarcomas. However, few have examined the overdiagnosis/overtreatment of benign uterine mesenchymal tumors that masquerade as uterine sarcomas. We report 4 cases of benign uterine mesenchymal tumors that were preoperatively diagnosed as having malignant potential and underwent extensive surgery. The patients had cotyledonoid-dissecting leiomyomas, uterine tumors resembling ovarian sex-cord tumors, metastasizing leiomyomas, and torsion of a subserosal uterine leiomyoma. The patients' ages ranged from 42 to 59 years (median 51.5). All 4 cases were suspected of having a malignant tumor based on preoperative clinical imaging, and 1 case was suspected of having a malignant tumor based on preoperative imaging and pathological evaluations of biopsy. All patients underwent surgery, including a hysterectomy. One of the 4 patients (25%) underwent lymphadenectomy, and 1 (25%) underwent partial lung resection. All patients survived without evidence of disease. Overall, detailed pre- and intraoperative clinical and pathological evaluations may be insufficient for diagnosis. Physicians should be aware of the diversity of uterine mesenchymal tumors, the difficulty in diagnosing them, and how to avoid these pitfalls.