Benign mixed tumors (pleomorphic adenomas) of the breast.

Six cases of benign mixed tumors of the female breast are described. The tumors were found in three settings: (a) as a de-novo lesion arising from breast parenchyma, (b) as single or multiple nodules arising in a background of benign proliferative epithelial elements, and (c) in association with breast carcinoma. The tumors ranged from 1 to 4 cm in diameter, and were histologically characterized by the admixture in various proportions of benign glandular epithelial and myoepithelial elements and cartilaginous or myxoid components. Immunohistochemical staining supported this interpretation. One of the cases was remarkable for the presence of abundant tyrosine-like crystals, a feature described in benign mixed tumors of salivary glands. None of the tumors has recurred during a follow-up period of 1-7 years. Mixed tumors of the breast are considered to be similar to their dermal and salivary gland counterparts.