The variable sonographic appearances of ovarian teratomas: correlation with CT.
To better understand how the internal composition of ovarian teratomas influences their sonographic features, we compared their sonographic and CT appearances in 23 cases. Sixteen lesions had a mixed echo texture, with hypoechoic as well as echogenic components; two were anechoic and five were entirely echogenic. Correlation with the CT images showed that the fat present in most teratomas had variable sonographic appearances. Pure sebum was anechoic or hypoechoic, but fat intermixed with hair strands was echogenic and often attenuated the sound beam because of the numerous tissue interfaces created within the mass. The hypoechoic component of the teratoma corresponded, on CT, to low-attenuation fat in 12 tumors and to fluid in five. Most teratomas contained a dermoid plug, a protuberance arising from the tumor wall and containing hair follicles and often fragments of bone or teeth. On sonography, all dermoid plugs were seen as an echogenic mass, often associated with distal acoustic shadowing and protruding into the hypoechoic portion of the teratoma. When the dermoid plug was large and occupied most of the tumor, the entire teratoma appeared echogenic, with no discernible anechoic component. We found that three factors greatly affected the sonographic appearance of ovarian teratomas: the size of the dermoid plug, the presence and location of calcified elements, and the histologic composition of the fatty component.