EP23.12: Ultrasound masks of not‐typical dermoid cysts: preoperative assessment of their malignancy risk and clinical‐surgical characteristics

Not-typical ovarian dermoid cysts are a category of ovarian tumours where preoperative ultrasound (US) diagnosis can be challenging and indeterminate. A retrospective, monocentric descriptive study. 3460 adnexal masses were diagnosed by US with subsequent surgical treatment and pathological examination during 8 year-period at the gynecological US reference centre. Within this cohort, 864 were identified as dermoid cysts, of which 788 were typical dermoid cysts, while 76 out of 788 (8.9%) dermoid cysts had not-typical US features. The simultaneous presentation of US and endoscopic images is crucial for enhancing the diagnostic proficiency and professional capabilities of the sonologist. The US characteristics of not-typical dermoid cysts varied widely, including features such as a homogeneous echogenic mass, intricate papillations-like inclusions, multiple septa and compartments, spherical anechoic inclusions, ground-glass echogenicity of the cyst content, diffuse suspension resembling “comets”, giant size, combination of not-typical features with typical dermoid cyst, invisible lesion indistinguishable from surrounding structures and colour score of 2-3 points. Preoperative assessment of malignancy risk according to the ORADS system was distributed as follows: ORADS 3 was observed in 5 patients, ORADS 4 in 30, ORADS 5 in 10, ORADS 0 in 5. Clinical and surgical characteristics of not-typical dermoid cysts included ovarian torsion in 9/76 patients, bilateral dermoid cysts in 5/76, recurrence of dermoids after their removal in 3/76, and anechoic spherical inclusions in large cysts (which corresponded to intracystic joint elements) in 2/76. In one case, a not-typical cyst had combined histological features of mature and immature teratoma. Pattern recognition and US expertise of an experienced sonologist are fundamental approaches in the preoperative diagnosis of not-typical dermoid cysts.