Ovarian endometrioma: a report of a pediatric case diagnosed prior to menstruation

Background Ovarian endometriomas (OEs) are rarely found in the pediatric population, especially before menstruation. We report a 6-year-old girl who was postoperatively diagnosed with OE before menstruation.Case presentation A 6-year-old girl presented to a local pediatrician with abdominal pain and vomiting. Abdominal ultrasonography revealed a multilocular cystic lesion to the left of the bladder. Magnetic resonance imaging (MRI) revealed similar findings, with the contents of the cyst showing a low signal on T1-weighted imaging and a high signal on T2-weighted imaging. The patient was referred to our institution for further examination. Enhanced computed tomography (CT) showed a multilocular cystic lesion sized 56 x 44 x 30 mm with partial calcification. The left ovarian vein was dilated, suggesting the origin of the tumor to be the left ovary. Extirpation of the lesion was performed under laparoscopic assistance. Pathological findings indicated an ovarian endometrioma. To our knowledge, this is the youngest report of an OE diagnosed in a patient prior to menstruation.Conclusions OEs in children before menstruation are extremely rare; thus, the long-term prognosis is yet to be determined.