Pancreatic neuropathy and neuropathic pain--a comprehensive pathomorphological study of 546 cases.
BACKGROUND& AIMS: Chronic pancreatitis (CP) and pancreatic adenocarcinoma (PCa) are characterized by intrapancreatic neural alterations and pain. Our aims were to: (a) Investigate whether neuropathic changes like pancreatic neuritis, increased neural density, and hypertrophy are phenomena only in CP or whether they are also evident in other pancreatic disorders as well, (b) study possible variations in neural cancer cell invasion among malignant pancreatic tumors, and (c) explore whether these neuropathic changes contribute to pain sensation. METHODS: Neuropathic changes were studied in PCa (n=149), in CP (n=141), in pancreatic tumors (PTm) including serous/mucinous cystadenomas, invasive/noninvasive intraductal papillary mucinous neoplasias, benign/malignant neuroendocrine tumors, ampullary cancers (n=196), and in normal pancreas (n=60). The results were correlated with GAP-43 expression, tissue inflammation, pancreatic neuritis, neural invasion, fibrosis, desmoplasia, pain, and patient survival. RESULTS: Increased neural density and hypertrophy were only detected in PCa and CP and were strongly associated with GAP-43 over expression and abdominal pain. The severity of pancreatic neuritis was strongest in PCa and was closely linked to changes in neural density and hypertrophy. The aggressiveness of neural cancer cell invasion was most prominent in PCa and was related to neuropathic changes, desmoplasia, and pain. Severe and enduring pain were strongly associated with poor prognosis in PCa patients. CONCLUSIONS: Enhanced neural density and hypertrophy are only typical features of CP and PCa among all investigated pancreatic disorders. Such neuropathic changes, including damage to nerves by inflammatory and/or cancer cells, seem to enhance and generate pancreatic neuropathic pain.