Background/purpose: Mucins are high molecular weight glycoproteins that have oligosaccharides attached to the apomucin protein backbone by O-glycosidic linkages. Here, we report the expression of MUC1 mucin (membrane-bound mucin), MUC2 mucin (intestinal-type secretory mucin), and MUC5AC mucin (gastric-type secretory mucin) in invasive ductal carcinomas (IDCs; n = 46) and intraductal papillary-mucinous neoplasms (IPMNs; n = 33) of the pancreas, and the relationship of this expression with malignant potential.
Methods: To clarify the precise expression pattern of mucins in IPMNs, we classified IPMNs into three histologic subtypes; IPMN-dark cell type ( n = 19), IPMN-clear cell type ( n = 10), and IPMN-compact cell type ( n = 4).
Results: IDC, with a poor outcome, showed a pattern of MUC1(+), MUC2(-), and MUC5AC(+ or -). In contrast, IPMN-dark cell type tumors, with a fairly favorable outcome, showed a pattern of MUC1(-), MUC2(+), and MUC5AC (+), and IPMN-clear cell type tumors, with a favorable outcome, showed a pattern of MUC1(-), MUC2(-), and MUC5AC(+). On the other hand, IPMN-compact cell type tumors showed a pattern of MUC1(+), MUC2 (-), and MUC5AC(+). In IPMN-dark cell type tumors with carcinomatous change showing invasive growth, the invasive areas acquired a characteristic of MUC1 expression that was usually seen in IDC, although their main noninvasive lesions showed no MUC1 expression. The IPMN-compact cell type tumors usually showed high cellular atypia and frequent MUC1 expression, even in the noninvasive areas.
Conclusions: Our study of the mucin expression pattern in IDC and IPMN shows that this pattern may be related to the biological behavior of pancreatic tumors and their malignant potential.