Two cases of primary breast carcinoma morphologically identical to low-grade mucoepidermoid carcinoma of salivary gland origin occurred. To our knowledge, this article represents the first description of this tumor type in the breast. Both lesions were well circumscribed, wholly or partially cystic, and composed of intimately associated, well-differentiated, squamous and mucinous glandular epithelium. It is suggested that these may represent an indolent tumor type in the breast analogous to their behavior in the salivary gland.