Carbon ion radiotherapy for recurrent malignant transformation from mature cystic teratoma of the ovary.

Mature cystic teratoma (MCT) is the most common tumor of the ovary; malignant transformation (MT) of squamous cell carcinoma is a rare disorder. A 78-year-old woman with stage IIc MT-MCT (squamous cell carcinoma [SCC]) underwent a total abdominal hysterectomy and bilateral salpingo-oophorectomy; there was residual tumor in the pelvis. The patient was treated with six courses of paclitaxel and carboplatin, but the recurrent tumor grew. The patient was then treated with carbon ion radiotherapy (CIRT). The recurrent tumor shrank and the patient has been free of clinical disease for 53 months. CIRT can be considered as a treatment for recurrent MT-MCT.