Perineural invasion (PNI) is defined as the presence of cancer cells along nerves and/or within the epineural, perineural and endoneural spaces of the neuronal sheath.Clinically, PNI is associated with increased tumor recurrence, poor survival after pancreatectomy and pain, an invalidating symptom that may impair quality of life. Pancreatic ductal adenocarcinoma has one of the highest incidences of PNI (70-100%) among all types of cancer, which correlates with a poor prognosis and decreased survival. PNI is a still not uniformly characterized or quantified event, usually it is described only dichotomously ("present" or "absent"), despite some efforts to use a more detailed scoring system. However, these scores are not specifically developed for pancreatic surgical specimen. Vascular invasion (VI), which is assumed to be associated with a more aggressive tumor biology and dissemination, lacks a specific scoring system as well. The primary aim of this study is to validate both retrospectively and prospectively a novel PNI and VI scoring system aimed at a more detailed stratification of perineural invasion, together with an accompanying scoring system for vascular invasion, and correlated them with disease free survival (DFS).
