Perineural spread (PNS) of tumour
Perineural spread (PNS) of tumour is a form of local invasion in which primary tumours cells spread along the tissues of the nerve sheath. It is a well recognised phenomenon in head and neck cancers.
An important distinction has to be made between Perineural invasion (PNI) and Perineural spread (PNS). PNI is a histological finding of tumor cells infiltrating or associated with small nerves (which cannot be radiologically imaged). PNS 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.
Perineural tumour 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 tumour spread) 4
Perineural tumour spread could be characterised as nerve thickening, widening of the neural foramen, loss of the fat surrounding the nerve and enhancement of the nerve after contrast administration.
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