"Perineural spread of tumour is a form of local invasion in which primary tumour cells spread along the tissues of the nerve sheath. It is a well-recognised phenomenon in head and neck cancers."
"oral cavity/laryngeal (2-30%) is more common than cutaneous (3-8%) SCC"
"An important distinction has to be made between perineural invasion (PNI) and perineural spread (PNS). The former is a histological finding of tumour cell infiltration or associated with small nerves that cannot be radiologically imaged, while the latter is macroscopic tumour involvement along a nerve extending away from the primary tumour; this can be radiologically apparent. A third term, neurotropism, simply means that a tumour has an affinity for growth along nerves."