Immunohistochemical studies on myoepithelial changes in breast tumors

Specific rabbit antisera directed against human uterine myosin were prepared and used for immunohistochemical studies on myoepithelial cells (MECs) in some breast tumors. In fibroadenomas, MECs were observed confined to the periductal portions but not in the stroma. In infiltrating duct carcinomas, MECs were also present as a distinctive periductal layer. Moreover, they were also seen in the infiltrating area, either associated with a small nest of carcinoma cells or freely in the stroma. Larger nests of medullary carcinomas usually were not accompanied by any layer of MECs. No MECs were detected in lobular carcinomas as far as the infiltrating area was concerned. It is suggested from these results that the behavior of MECs is significantly different, depending upon the types of breast tumors. It also appears that the present method may be useful for further analysis of the origin and growth pattern in various breast tumors.