Dedifferentiated carcinoma is rare endometrial carcinoma containing both differentiated carcinoma and undifferentiated carcinoma. We report a case of uterine dedifferentiated carcinoma with multiple tumor embolisms. A total abdominal hysterectomy, bilateral salpingo-oophorectomy, and tumor embolism resection was performed. Paclitaxel-carboplatin chemotherapy as the adjuvant chemotherapy was refractory, and she died 4 months after the operation.

A medical condition in which cancer patients present with rheumatoid-like symptoms such as arthritis, myalgia, and muscle weakness is called paraneoplastic rheumatic syndrome (PRS). Paraneoplastic syndrome may cause various symptoms other than encephalitis, and we would like to report a case of presumed tumor-associated syndrome in which an ovarian teratoma was found during a thorough examination of arthralgia and the symptoms improved after removal.

She was 18 years old. A CT scan revealed a 12 cm mature teratoma of the left ovary. After removal by laparoscopic surgery, subjective symptoms such as joint pain improved and inflammatory markers improved.

Three years and eight months have passed since the surgery, and the patient is doing well without any symptoms such as joint pain. Ovarian teratomas have been reported to cause symptoms associated with various organs, including encephalitis, and it is important to screen patients with unexplained arthralgia for the possibility of tumor-associated symptoms due to ovarian tumors.