Peak density of immature nerve cells occurs with high-grade dysplasia in intraductal papillary mucinous neoplasms of the pancreas.

The development of neural structures within tumors is now considered vital for carcinogenesis. However, the time course of this development in human pre-invasive neoplasia has been incompletely described. Therefore, we performed a detailed analysis of nerves across the neoplastic spectrum in resected intraductal papillary mucinous neoplasms (IPMNs) of the pancreas. Histology and multiplexed immunochemistry demonstrated that nerve density increased from low-grade (LG) to high-grade dysplasia (HG) but did not further increase once invasive IPMN (INV IPMN) was present. Higher nerve density correlated with increasing expression of nerve growth factor (NGF) by the tumor cells. Intra-tumoral nerves were immature and lacked markers of sympathetic, parasympathetic, and sensory lineages. Here, we show for the first time the presence of neural precursor cells (NPCs) within the stroma of pancreatic tumors. The density of these doublecortin (DCX)-positive NPCs increased from LG to HG, but not from HG to INV IPMN. We conclude that peak neural density of tumors is reached in high-grade dysplasia (often termed carcinoma in situ) rather than after invasion. These findings suggest that nerve-tumor interactions are important in IPMN progression and may serve as the basis for future mechanistic studies and novel therapeutic modalities.