Mammary ductal foam cells: macrophage immunophenotype.

Mammary ductal foam cells are present in normal breast tissue as well as in a number of breast diseases. Such foam cells tend to be in particular abundance with fibrocystic changes of the breast. Foam cells may appear within duct lumens or plastered in cohesive masses along duct walls, simulating an epithelial structure. The nature and origin of these innocuous-appearing cells, based on morphologic studies, remain a controversy, for they appear to be of epithelial derivation. This study was undertaken to determine the nature of intraductal "foam" cells and their origin in the breast. Nine cases of adult fibrocystic disease were examined immunohistochemically with antibodies to cytokeratins (Mak-6, Cam 5.2), leukocyte common antigen, and the following macrophage antibodies: KP-1 (CD68), HAM 56, and MAC 387. The lysozyme and alpha-1-antitrypsin content of foam cells also was studied. The immunohistochemical data in this study confirm the macrophage character of these foam cells, which are positive for CD68, HAM 56, and MAC 387, lysozyme, and alpha-1-antitrypsin and negative for leukocyte-common antigen and cytokeratins.