Ultrasound in the diagnosis of ovarian dermoid cysts: a pictorial review of the characteristic sonographic signs

Dermoid cysts (mature cystic teratoma) are the commonest germ cell neoplasm and in some series the most commonly excised ovarian tumour. They are composed of tissue from at least two of the germ cell layers and often contain hair, sebum and teeth. These tumours show a wide range of ultrasonic appearances because of their variable composition. On account of this they may mimic a variety of other pelvic masses. In many cases, however, the ultrasonic appearance can be distinctive, and a number of sonographic signs characteristic of dermoid cysts have been described. Typical appearances include a shadowing echodensity or dermoid plug; diffuse or regional high amplitude echoes; the tip of the iceberg sign; dermoid mesh; fat-fluid levels and intracystic floating balls. When two or more characteristic signs are present, a high positive predictive value and a confident sonographic diagnosis can be achieved. We present a pictorial review of the characteristic sonographic signs helpful in making the diagnosis of ovarian dermoid cyst. We also discuss the pitfalls of making an ultrasound diagnosis, and illustrate some of the conditions that may mimic dermoid cysts. We include correlation with computed tomography and magnetic resonance imaging where appropriate.