Endometrioma with calcification simulating a dermoid on sonography

Several investigators have explored the sonographic diagnostic criteria of endometriomas. Endometriomas have characteristic findings on sonography. Diffuse dispersion of low-level echoes within a cystic mass is thought to be the most useful diagnostic feature. Mais et al documented sensitivity of 88% and specificity of 90% in differentiating endometriomas from other ovarian masses with endovaginal sonography. Patel et al identified diffuse low-level internal echoes in 95% of endometriomas and 19% of nonendometriomas. The presence of multilocularity or hyperechoic wall foci further increased the possibility of a given mass being an endometrioma. They postulated that these two findings would have the highest diagnostic value in distinguishing endometriomas from other adnexal masses. This report presents an unusual case in which a large cystic adnexal mass showed a fluid-fluid level and a large, discrete calcification. A sonographic diagnosis of a dermoid was made; however, it proved to be an endometrioma on magnetic resonance imaging (MRI), which was later confirmed with laparoscopic removal and a pathologic report.