Palisaded encapsulated neuroma (PEN, also known as solitary circumscribed neuroma) is a slow-growing, benign, solitary, spontaneous papule secondary to the proliferation of nerve fibers encapsulated within the perineurium (hence its encapsulation). There is no clear etiology. Often PEN favors the face (including the oral cavity and nasal fossa), particularly near a mucocutaneous junction, but it can also appear on the neck, genitalia, trunk, extremities, hands, and feet. It is most common in adults over the age of 40 and has no significant sex predominance. There is typically no inciting trauma.

Rare cases of multiple PENs have been reported.