OC025: Ultrasound characteristics of typical and atypical endometriomas

To define which US characteristics are suggestive for endometriosis and with which ultrasound features “atypical” endometriomas (Eomas) present. The IOTA study included 3513 patients with an adnexal mass. Histologically proven Eomas were included, a unilocular mass with ground glass echogenicity was called “typical” and other morphologic features “atypical”. 710/3513 masses (20%) proved to be endometriosis; 52% had “typical” and 48% “atypical” US features. Atypical Eomas were unilocular (28%), unilocular-solid (17%), multilocular (37%), multilocular-solid (15%) or solid (3%). The median of the max diameter of the lesion was 59 mm and the median of the max diameter of the solid component was 17 mm. Echogenicity was other than ground glass in 67%. Papillary projections were present in 21%, in 71% of them there was only one papillarity present and in 26% there was flow on CD examination. We conclude that Eosis is likely in the presence of: 1. unilocular mass with ground glass echogenicity, 2. unilocular-solid mass with ground glass echogenicity and a papillary projection without internal flow, and 3. multilocular mass with ground glass echogenicitiy. Applying these rules retrospectively to the total IOTA dataset gave a sensitivity of 67.9% and a specificity of 97%. 416/3513 were unilocular with ground glass appearance, 88% proved to be Eomas, 6/49 (1.4%) that were no Eomas were malignant. 36/3513 were unilocular-solid with a papillary projection with no internal flow and ground glass appearance, 72% were Eomas and 2/10 (5.6%) that were no Eomas were malignant. 120/3513 were multilocular with ground glass appearance, 74% were Eomas and 6/31 (5%) that were no Eomas were malignant. Not only a unilocular mass with ground glass echogenicity is suggestive for Eosis. Common findings also include a unilocular-solid mass with ground glass echogenicity and a papillarity without internal flow, and a multilocular mass with ground glass echogenicitiy.