An epidermoid cyst, also known as a sebaceous cyst (a misnomer), is a semi-solid cyst filled with keratin. The cysts are lined by keratinizing epithelium that is responsible for the soft "cheesy" keratin contents. The epidermal cyst is a common lesion that can arise on the face, trunk, extremities, or vulva. The cyst wall is stratified squamous epithelium, and the content is formed of macerated keratin and lipid-rich debris. The lesion may be asymptomatic, but rupture can result in significant discomfort.