Deep penetrating nevus (DPN), also known as a plexiform spindle cell nevus, is a darkly pigmented melanocytic lesion that most often appears as an asymptomatic solitary papule or nodule on the head or neck, trunk, or upper extremities. The DPN is often described by patients as a new or changing lesion, since it is almost always acquired during life. It usually arises before age 30, and less than 5% of DPN develop after the age of 50. DPN are more common in females than males, and there is no association with a family history of melanoma.

Clinically and histopathologically, DPN can be confused with malignant melanoma since it can arise with sudden onset, have a darkly pigmented appearance, and have cytologic pleomorphism with deep infiltration of the dermis. Dermatopathologists thus face the primary challenge of differentiating between DPN and malignant melanoma, as well as other melanocytic lesions.

DPN are generally considered benign, although rare cases of recurrences have been noted as well as spread to regional lymph nodes, mostly in the setting of having atypical histopathologic features.