Mucinous cystadenoma arising 3 years after ovarian-sparing surgery for mature teratoma in a child

We report the case of a 15-year-old girl diagnosed with mucinous cystadenoma 3 years after ovarian-sparing surgery for a mature teratoma located in the same ovary. Ovarian teratoma is the most common ovarian neoplasm in children, whereas mucinous cystadenoma is extremely rare during childhood.