MAINTENANCE OF POLARITY AND A DUAL CELL-POPULATION IN ADENOID CYSTIC CARCINOMA OF THE BREAST - AN IMMUNOHISTOCHEMICAL STUDY

Aims: Adenoid cystic carcinoma (ACC) of the breast, although quite unc ommon, is histologically distinct and has an excellent prognosis, Our purpose was to characterize molecular markers of cellular differentiat ion and polarity to define better the role that these combined feature s might play in the excellent prognosis of ACC in this site. Methods a nd results: We performed immunohistochemical stains for expression of vimentin (VM), cytokeratin (CK), smooth muscle actin (SMA), laminin (L AM), E-cadherin (E-cad), beta-catenin (beta-cat) and fodrin in 14 exam ples of ACC. Two types of intercellular lumens and defining lining cel ls were detected: true epithelial lumens were lined by CE: positive ce lls that maintained the normal glandular luminal cells with an intact polarity and basolateral membrane compartment indicators: fodrin, E-ca d and beta-cat. The second type of intercellular space was a pseudolum en, surrounded by myoepithelial cells that were strongly positive for VM and SMA, and lined by LAM. Double staining for VM and CK, VM and SM A, and CK and SMA detected occasional cytoplasmic co-expression of the se markers in the myoepithelial cell compartment, but VM and SMA did n ot stain epithelial lumenal cells, Conclusions: ACC of the breast is c haracterized by the presence of two types of intercellular lumens, one conserving basolateral markers of normal polarity (epithelial) with t he other containing basement membrane material (abutted by myoepitheli al cells). Dominance of VM staining may be a hallmark of ACC, along wi th maintained epithelial and myoeithelial compartments. This status of advanced, normal differentiation despite local invasion may be respon sible for lack of distant metastasis.