Perineural spread of tumor
Perineural spread of tumor is a form of local invasion in which primary tumors cells spread along the tissues of the nerve sheath. It is a well-recognized phenomenon in head and neck cancers.
An important distinction has to be made between perineural invasion (PNI) and perineural spread (PNS). The former is a histological finding of tumor cell infiltration or associated with small nerves that cannot be radiologically imaged, while the latter is macroscopic tumor involvement along a nerve extending away from the primary tumor; this can be radiologically apparent. A third term, neurotropism, simply means that a tumor has an affinity for growth along nerves.
Perineural tumor spread is more frequently associated with 1,2,5:
- mucosal/cutaneous squamous cell carcinoma
- oral cavity/laryngeal (2-30%) > cutaneous (3-8%)
- most common overall 5
- salivary gland carcinoma
- mucosal/cutaneous basal cell carcinoma (2-5% demonstrate perineural tumor spread) 4
- meningioma (rare) 6
Perineural tumor spread could be characterized as nerve thickening, widening of the neural foramen, loss of the fat surrounding the nerve and enhancement of the nerve following contrast administration.