MUC‐1 mucin expression in invasive areas of intraductal papillary mucinous tumors of the pancreas

Abstract

The expression of MUC‐1 mucin (membrane‐associated mucin) and MUG2 much (secretory mucin) were immunohistochemically examined in 46 invasive ductal carcinomas (IDC) and 16 intraductal papillary mucinous tumors (IPMT) of the pancreas. lntraductal papillary mucinous tumors usually reveal expansive growth. However, of the 16 IPMT examined in the present study, three showed an invasive growth pattern, which was similar to ‘mucinous carcinoma’, around the non‐invasive growth areas. Of 46 IDC, MUCl much detected by monoclonal antibodies, DF3 and MY.1E12, was expressed in 44 cases (96%) and in 45 cases (98%), respectively, whereas MUC‐2 mucin detected by polyclonal antibody, anti‐MRP, was not expressed in any of the cases (0%). In contrast, in the non‐invasive growth areas of the 16 IPMT, MUG1 much detected by DF3 and MY.1 E12 was expressed in four cases (25%) and in six cases (38%), respectively, whereas MUG2 mucin detected by anti‐MRP was expressed in 13 cases (81%). The invasive growth areas of the three IPMT showed positive expression of MUG‐1 mucins detected by DF3 and MY.1E12, although the non‐invasive growth areas showed negative expression of MUG1 muclns, except for their focal positive expression in one of the three cases. These findings indicate that the invasive growth areas of IPMT acquire a characteristic of MUC‐1 much expression that is usually seen In IDC.