A Distinctive Histological Form of Squamous Cell Carcinoma With Perineural Invasion.

A modest proportion of individuals diagnosed with squamous cell carcinoma (SCC) display perineural invasion (PNI), the neoplastic invasion of one or more nerves. It is associated with a marked increase in mortality in patients with SCC and is oftentimes only diagnosed after a significant invasion occurs. An 84-year-old male, otherwise in good health, presented to us with a fast-growing, 3-cm nodule on his right malar region associated with paresthesia and radiating pain. Biopsy of the lesion revealed moderately differentiated infiltrative squamous cell carcinoma, which was later discovered to involve the perineural fascia of the trigeminal nerve. Excision of the infraorbital nerve and maxillary bone was performed to remove the tumor, with the resulting defect later reconstructed. Here, we present findings of SCC with unique histological features predictive of potential PNI. These features include a rim of cuboidal cells which quickly transition into a well-differentiated, eosinophilic parakeratotic core, reminiscent of a "fried egg" appearance. Awareness of these histological findings may allow clinicians to detect PNI in patients with SCC before widespread and irreversible involvement.