Nerves and neurotropic carcinomas.

Neurotropism by a carcinoma in the head and neck refers to invasion in, around, and through peripheral nerves. This invasion may be along planes of least resistance in the connective tissue coverings of the nerve or less frequently by endolymphatic spread. The only lymphatics associated with a nerve are those in the perineural covering and in the epineurium. Such malignant neurotropism is to be distinguished from benign epithelial inclusions simulating neural invasion.