A case of recurrent squamous cell carcinoma showing perineural invasion of the facial nerve

The high-risk factors of cutaneous squamous cell carcinoma (cSCC) include size (>2 cm), thickness/depth of invasion (> 4 mm), recurrent lesions, the presence of perineural invasion (PNI), location near the parotid gland, and immunosuppression. These patients have a higher risk (>10-20%) of developing metastases to regional lymph nodes based both on unfavorable primary lesions and also patient factors. Among the risk factors, the PNI is often underappreciated by clinicians and is not well documented in the literature. But it is also important that clinicians treating cSCC have an understanding and awareness of PNI. We report a case of recurrent squamous cell carcinoma showing PNI of the facial nerve and review current concepts of PNI.