Size threshold as a risk for malignant transformation in typical ovarian dermoid lesions: a scoping review

Purpose The O-RADS malignancy risk stratification of typical ovarian dermoid cysts by using a 10 cm threshold is based on expert consensus rather than analysis of objective clinical data. This comprehensive scoping review consolidated all currently available studies evaluating typical benign ovarian dermoid cyst size and risk for malignant transformation. Methods A systematic review of MEDLINE, Embase, Scopus and the Cochrane library was performed from inception to January 14, 2024, using PRISMA-ScR guidelines. A grey literature search and forward searching of reference lists from included studies were performed. Case reports and case series evaluating dermoid cyst size and malignant transformation as defined by a pathological reference standard were included. Data synthesis was provided as a qualitative review of the existing literature. Results Twenty-five studies were included in qualitative synthesis comprising 6 case reports and 19 retrospective studies with a total of 15,295 dermoid cysts. Of these, 215 lesions demonstrated malignant transformation. Studies reporting dermoid size with malignant transformation ranged from 1 to 32 cm with 46/173 (27%) total malignant transformation lesions measuring < 10 cm. Solid enhancing components were infrequently reported but all measured > 1 cm when described. Conclusion More than 25% of dermoid cysts with malignant transformation may be classified as "almost certainly benign" with the current 10 cm O-RADS malignancy risk threshold. Although surveillance of O-RADS 2 dermoid cysts may improve sensitivity, modifying a caveat recommendation for MRI O-RADS +/- gyn-oncologist referral when potentially solid components are present in otherwise typically benign dermoid cysts may be appropriate.