How do epidermal inclusion cysts (EIC) form?

Updated: Sep 17, 2020
  • Author: Linda J Fromm, MD, MA, FAAD; Chief Editor: Dirk M Elston, MD  more...
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Answer

Epidermoid cysts likely form by several mechanisms. They may result from the sequestration of epidermal rests during embryonic life, occlusion of the pilosebaceous unit, or traumatic or surgical implantation of epithelial elements. HPV infection, ultraviolet exposure, and eccrine duct occlusion may be additional factors in the development of palmoplantar epidermoid cysts. [29] HPV has also been identified in nonpalmoplantar epidermoid cysts.

Congenital epidermoid cysts of the anterior fontanelle or those that are orogenital in location presumably result from sequestration or trapping of epidermal rests along embryonic fusion planes during development. Lip and lingual lesions may be related to aberrant fusion of the branchial arches, while genital lesions may result from improper closure of the genital folds.

Any benign or malignant process affecting or growing near the pilosebaceous unit may lead to occlusion or impingement of the follicular ostia with subsequent formation of a cyst. Cysts with an acneiform distribution are likely the result of follicular occlusion. In elderly persons, accumulated sun damage can injure the pilosebaceous unit, causing abnormalities such as comedonal plugging and hypercornification, both of which can eventuate in cyst formation. [30] This condition is referred to as Favre-Racouchot syndrome.


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