Dermoid cyst

A dermoid cyst is a teratoma that contains developmentally mature skin, with hair follicles and sweat glands, sometimes luxuriant clumps of long hair, and often pockets of sebum, blood, fat, bone, nails, teeth, eyes, cartilage, and thyroid tissue. Because it contains mature tissue, a dermoid cyst almost always is benign. The rare malignant dermoid cyst usually develops squamous cell carcinoma.

Some authors use the term dermoid cyst as a frank synonym for teratoma, meaning any teratoma, regardless of its histology or location. Others use it to mean any mature, cystic teratoma. These uses appear to be most common in gynecology and dermatology.