Intraductal Papillary Mucinous Neoplasm: New Insights Into Its Origin and Nomenclatures

Mucinous cells can be detected sporadically or may constitute the primary tumor component in salivary gland tumors, as observed in the intraductal papillary mucinous neoplasm (IPMN). This low-grade tumor is composed of mucinous columnar cells organized into papillary cystic structures. The present study aimed to compare the mucous cells in IPMN with mucous cells present in mucoepidermoid carcinoma (MEC) and papillary cystadenoma (PC). Immunohistochemistry analysis was carried out to compare the mucous cells in IPMN with the sporadic mucous cells in MEC (n = 4) and PC (n = 3). The results indicated that IPMN cells were positive for CK7, CK18, DOG1, and NKX3.1 and negative for CK14, SMA, and p63. The mucous cells in both MEC and PC were positive for CK7 and negative for CK18, SMA, DOG1, and NKX3.1. The positive expression of CK14 and p63 revealed the presence of basal cells both in PC, cystic areas of MEC, and normal mucous salivary glands. The immunohistochemical profile of IPMN closely resembles that of the mucous cells of the minor salivary glands yet differs from the mucous cells observed in MEC and PCX. This suggests that IPMN is probably derived from the transformation of secretory cells of the minor mucous salivary gland and has no rimming/basal cells. For this reason, we propose that this tumor is designated as mucous acinic cell carcinoma.