A group of uncommon neoplasms, usually seen in the salivary glands but occurring in the breast, with a variable clinicopathologic spectrum and divided into those with myoepithelial differentiation and those without. This group includes mammary adenoid cystic carcinoma, adenoid cystic carcinoma, mucoepidermoid carcinoma, acinic cell carcinoma, polymorphous low-grade adenocarcinoma and oncocytic carcinoma.