Innervation of the pancreas from the perspective of perineural invasion of pancreatic cancer

Introduction: Pancreatic cancer invasion via neural routes (perineural invasion) has been studied extensively, but detailed research on the morphology of innervation of the pancreas related to perineural invasion is scarce. Aims: To clarify the morphology of neural distribution in the human pancreas. Methodology: The pancreas and surrounding structures were dissected in 9 cadavers, the specimens were immersed in a 0.001% solution of alizarin red S in ethanol to stain the peripheral nerves, and the detailed distribution was studied to confirm the extrapancreatic and intrapancreatic plexus using a binocular microscope. Results: The innervation of the uncinate process of the pancreas originated from the superior mesenteric plexus (SMPlx) along the inferior pancreaticoduodenal artery (IPDA), but did not form a wide offshoot of nerve bundles as reported. Concerning the innervation of the body and tail, it was found that the nerve fibers entered the pancreas immediately after leaving the celiac plexus, and were distributed around the pancreatic duct in a twig-like manner. Conclusion: It was emphasized that the nerve originating from SMPlx to the uncinate process chiefly ran along the IPDA and it was necessary to focus one's attention not only on the extrapancreatic perineural invasion but also on the intrapancreatic perineural invasion in carcinoma of the body and tail of the pancreas.