What causes an inclusion cyst to come to a head and rupture, and what effect does this have?—JUDIE HARTLEY, CRNP, BSN, Warren, Ohio

An epidermal inclusion cyst or epidermoid cyst is lined with keratinizing epithelium that contains a granular layer. The cyst may become inflamed following local trauma, and keratin production by the cyst lining may be stimulated, resulting in an increase of both the cyst’s content and size. Subsequently, the cyst may rupture (spontaneous or patient-induced) or be incised (by appropriate medical or surgical personnel). Ideally, the latter procedure allows evacuation of the cyst contents without additional dermal inflammation. Although the contents of a cyst are diminished after it has ruptured, the keratin within the cyst or its wall may extend into the adjacent dermis, where it is recognized as a foreign body and often elicits an additional inflammatory response. — Philip R. Cohen, MD (144-4)

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