Have you noticed that perineural invasion is being reported more than it used to be? I asked Associate Professor Matthew Foote to help me tackle this tricky issue. Matthew is a Radiation Oncologist. He is known around the world for his skill in treating skin cancer with radiation.
Associate Professor Matthew Foote
But first, a bit of background:
Perineural invasion (PNI) refers to when a cancer has spread to a nerve. This is often associated with a worse prognosis. Perineural invasion may be symptomatic or asymptomatic/incidental. Symptomatic PNI (e.g. pain, tingling) is a huge topic and is outside the scope of this newsletter. What I want to cover is incidental PNI. This is where a skin cancer is cut out and PNI is reported but the patient has no symptoms. This is an example histology report showing incidental PNI:
The question is – when should you refer these patients for post-operative radiotherapy? Cancer Council Australia says that “no further intervention is required if pathological examination shows that the perineural spread is limited to small dermal nerve fibres <0.1mm, and the tumour has been completely excised with a wide resection margin.” This is based on a study which found that no disease-specific deaths occurred in patients with PNI <0.1mm. Patients with PNI of 0.1mm or greater had a significantly higher rate of nodal metastasis and death.
So what’s the definition of a “wide resection margin”? Is referring for radiation as simple as using this 0.1mm cut off?
Until next time,
NS
