Perineural Invasion (PNI)

Compartment: Reticular Dermis

Illustration of malignant tumor cells encircling and invading a peripheral nerve, with a clear retraction space around the tumor-nerve complex.
Perineural invasion: tumor cells surrounding a peripheral nerve, a high-risk histologic feature.

Definition: Spread of malignant tumor cells along or around a peripheral nerve — a high-risk feature linked to recurrence and aggressive behavior.

Clinical Context: Cutaneous squamous cell carcinoma, Basal cell carcinoma, Desmoplastic melanoma, Microcystic adnexal carcinoma

Key Feature: Tumor cells wrapping ≥50% of the nerve circumference, often with a clear retraction artifact around the tumor-nerve complex.

🔗 Related Terms: Verocay Body