Histologic mimics of perineural invasion

Background Perineural invasion (PNI) by primary cutaneous cancers is an important adverse risk factor. Certain benign conditions may mimic microscopic PNI. Mohs surgery is being performed more frequently on smaller primary cutaneous malignancies. While PNI may be present in these cases, it is likely to be microscopic and asymptomatic, affecting as little as one cutaneous nerve branch. Methods Review of the literature base regarding PNI as well as contribution of original findings. Results Four benign entities that could easily be confused with microscopic PNI are presented. Conclusion At least four benign mimics of microscopic PNI exist, important in the differential diagnosis of microscopic PNI. Knowledge of these entities should help dermatopathologists to correctly distinguish them from PNI and avoid unnecessary additional treatment.