SMAD4 and pancreatic intraductal papillary-mucinous neoplasm: The upregulation of FST, but not of TGF-β in IOPN, compared to IPMN/IPNB in the present study may suggest that the downregulation of activin pathway via FST, but not TGFβ-SMAD4 pathway, is related to IOPN formation.