What is the cause of this patient's longstanding abdominal discomfort?
Large pelvic cystic mass, likely ovarian cystadenoma.
T2 hyperintense and T1 hypointense, large (23 x 10 cm) well defined cystic mass arising from the pelvis (most likely from left ovary). There are no thick internal septations, papillary projections, solid component, nor evidence of peritoneal dissemination of disease.
Based on the lesion size and the morphologic features, ovarian cystadenoma was the favoured diagnosis, with potential differential of a simple cyst or a borderline serous neoplasm.