F-18 FDG PET/CT of a Uterine Smooth-Muscle Tumor of Unknown Malignant Potential

We report a patient who was found to have a smooth-muscle tumor of unknown malignant potential on F-18 FDG PET/CT. A 49-year-old woman was admitted because of abdominal distension of 6-month duration. CT showed a 10 × 17 × 19 cm mass at the posterior side of the uterus displacing the uterus to the right anterior side, which was thought to be a subserosal myoma or a leiomyosarcoma originated from the uterus. F-18 FDG PET/CT showed a large mass demonstrating heterogeneous FDG uptake. Total abdominal hysterectomy, bilateral salpingo-oophorectomy, and pelvic lymphadenectomy were performed. The mass was diagnosed as a smooth-muscle tumor of unknown malignant potential.