Tip of the iceberg sign (ovarian dermoid cyst)
Tip of the iceberg sign refers to one of the characteristic appearances of an ovarian dermoid cyst. If there are echogenic cyst contents of sebum and hair, they cause marked posterior acoustic attenuation so that only the superficial part of the cyst is seen. Just like an iceberg, you may only be able to see a small piece of the structure, with a much larger piece deeper.
The intense acoustic shadowing in an ovarian dermoid may also be caused by calcifications (such as teeth) or by fat in a Rokitansky nodule if present.