Histopathological features of clinical perineural invasion of cutaneous squamous cell carcinoma of the head and neck and the potential implications for treatment.

BACKGROUND: Nonmelanoma skin cancer (NMSC) with perineural invasion (PNI) is most commonly seen in cutaneous squamous cell carcinoma of the head and neck (SCCHN). The cranial nerves are a conduit for skin cancer to reach the brainstem.
METHODS: The histopathological features of 51 tissue specimens from 49 patients with cutaneous SCCHN and clinical PNI were assessed with consecutive transverse and longitudinal sections.
RESULTS: No skip lesions were identified. Tumor spread was contiguous in all specimens. No tumor spread into the perineural space from surrounding or adjacent tumor was seen. Proximal large cranial nerves showed epineural involvement in 3.9% in areas with large tumor bulk, extensive PNI, and intraneural invasion.
CONCLUSION: Perineural tumor spread in cutaneous SCCHN was contiguous and no skip lesions were evident in nerve specimens assessed in this series. Spread beyond cranial nerve perineurium was uncommon, reflecting its multilayer barrier function at this level. These findings may have treatment implications.