Introduction/Background The most common signs of BOT on ultrasound (US) are reported to be: a septate cyst with solid component and/or mural nodules containing blood vessels in papillary projections. However, we describe ultrasonographic markers additional for the diagnosis of BOT

Methodology A retrospective study at a tertiary referral university hospital with a gynaecological oncology unit, from patients who underwent surgery between 2012 and 2022 with previous transvaginal ultrasound performed by gynaecologists or radiologists. Patients with a diagnosis of BOT by histopathological findings were included. Descriptive analyses were performed.

Results Of 18 patients diagnosed with BOT, with a mean age of 39 (±) 17 years, 11 (73%) were premenopausal, their median CA 125 was 115 (±) 32 U/mL. The mean maximum diameter of the lesion was 54 (±) 72 mm, 9 (60%) were described as unilocular solids, 5 (33%) as multilocular solids and 1 (7%) as unilocular. In addition to the classic criteria such as vascularization in the papilla found in 15 (83%) of the cases, we found novel characteristics such as: a low level of echogenicity content in 14 (78%) and a pattern of microcystic tissue that resembles a group of small bubbles in 12 (67%) of these tumors. Furthermore, when these three characteristics were positive, the tumors were diagnosed by histopathology as being of serous origin.

Conclusion This study proposes additional characteristics that are of interest for the approach and diagnosis of BOT by ultrasound.