Borderline epithelial ovarian tumors (BEOT) are characterized by cellular proliferation with mild nuclear atypia, but without destructive stromal invasion. Preoperative diagnosis of BEOTs is important because treatment strategy is different from that for benign and malignant tumors. Although MR is the established method for characterization of ovarian masses, CT and PET can also provide useful information for the diagnosis of BEOTs. Learning objective of this presentation is to describe useful multimodality imaging findings correlated with pathological findings and pitfalls in the diagnosis of BEOTs, as well as to describe the revised points in the WHO 2020.

1, MR imaging findings of BEOTs and radiologic-pathologic correlation - Serous borderline tumor - Seromucinous borderline tumor - Mucinous borderline tumor - Clear cell borderline tumor - Endometrioid borderline tumor - Borderline Brenner tumor - Peritoneal implant 2, Multimodality diagnosis of BEOT - Role of CT - Role of PET 3, Pitfalls - Benign lesions mimicking BEOT - Malignant lesions mimicking BEOT