MedGen

Trichilemmal cysts, also known as pilar cysts or tricholemmal cysts, are derived from the outer root sheath of the deeper parts of a hair follicle and consist of a well-keratinized epidermal wall surrounding semisolid hair keratin. They occur predominantly on the scalp, are easily enucleated, and appear as a firm, smooth, white-walled cyst without a punctum (McGavran and Binnington, 1966; Pinkus, 1969; Leppard and Sanderson, 1976). [from OMIM]

Steatocystoma multiplex is a skin disorder characterized by the development of multiple noncancerous (benign) cysts known as steatocystomas. These growths begin in the skin's sebaceous glands, which normally produce an oily substance called sebum that lubricates the skin and hair. Steatocystomas are filled with sebum.

In affected individuals, steatocystomas typically first appear during adolescence and are found most often on the torso, neck, upper arms, and upper legs. These cysts are usually the only sign of the condition. However, some affected individuals also have mild abnormalities involving the teeth or the fingernails and toenails. [from MedlinePlus Genetics]

A rare large, multinodular, usually benign, tumor that is generally located in the posterior part of the scalp in aged women (over 50 years). It first appears as a painless nodule that later grows into a solid or partially cystic tumor that is mobile over the underlying subcutaneous tissues. It can present ulceration, inflammation or even bleeding and can cause necrosis of the adjacent tissues. [from ORDO]

Nontender, round and firm, but slightly compressible, intradermal or subcutaneous cyst measuring 0.5-5 cm in diameter. Epidermal cysts are intradermal or subcutaneous tumors, grow slowly and occur on the face, neck, back and scrotum. They usually appear at or around puberty, and as a rule an affected individual has one solitary or a few cysts. [from HPO]

Nontender, round and firm, but slightly compressible, intradermal or subcutaneous cyst measuring 0.5-5 cm in diameter. Trichilemmal cysts are acquired rather than congenital, and tend to appear on the scalp rather than the face, and to be intradermal rather than subcutaneous. [from HPO]