- Male predominance; most common in the anogenital region. Also found on the scalp, upper extremities and trunk.
- 20% incidence of carcinoma
- Multilocular epidermal inclusion cyst-type cystic spaces containing keratinous material within the dermis, sometimes connecting to the epidermis through a narrow opening
- Epidermal-type keratinization must be present in order to make this diagnosis.
- Suamous eddies may be seen.
- The squamous epithelium may extend somewhat into the adjacent dermal stroma, but the lesion remains relatively circumscribed unless carcinomatous change has occurred.