MMP9 and neoplasm: This allowed us to identify potential core genes in PanNET stroma (COL1A1, COL1A2, COL3A1, COL5A1, COL5A2, COL6A3, and FN1) and tumor (RBP4, SPINK1, PLA2G1B, EGR1, and CD99), outlay the altered molecular pathways and pinpoint the potential mechanisms of crosstalk between tumor and stroma (PDGF/PDGFR axis, NOTCH3, MMP9).