Among these are invasive breast carcinoma of no special type (IC-NST, formerly known as invasive ductal carcinoma), invasive lobular carcinoma (ILC) which comprise 8–15% of all breast tumors, and mucin-secreting mucinous breast cancers (MBC; >90% mucin) that comprise ~4% of all breast cancers. Here, MUC5AC is linked to invasive ductal breast carcinoma.