Path proven ovarian serous borderline tumor.  This case demonstrates the typical appearance of a unilocular lesion with papillary projections.

Based on IOTA simple rules, this is an indeterminate lesion, which contains both "B" features (B1 - unilocular) and "M" features (M3 - more than 3 papillary projections and M5 - strong color flow).

ADNEX model predicts a 73% chance of benign lesion.

O-RADS Category 5 - High risk of malignancy: Unilocular cyst, ≥ 4 papillary projections, any size, CS = any.

Note here discordance between the IOTA, ADNEX, and O-RADS.