Radiological appearances of dermoid tumours (with emphasis on fat fluid levels)

Nine cases of dermoid tumours, one in the chest and eight in the abdomen are reported with various radiological findings on plain films, ultrasound and computed tomographic (CT) scans. The various radiological appearances at ultrasound and CT are described. The incidence and frequency of fat-fluid interfaces on ultrasound and CT scans are highlighted. Since the appearances of fat on ultrasound are variable, CT is therefore more specific in showing in fat-fluid levels. Moreover the dermoid tissue plugs seen on CT and ultrasound scans, with their surrounding fat, are highlighted as the so-called "iceberg" sign or as "target" signs. The paper concludes that the presence of fat fluid levels, a finding not previously emphasized, with a positive "iceberg" or "target" sign on CT or ultrasound scans, are pathognomonic of dermoid cysts.