Immunoperoxidase localization of lactalbumin in malignant breast neoplasms.

By an immunoperoxidase method, lactalbumin was demonstrated in the cytoplasm of epithelial cells of normal breast, primary and metastatic breast carcinomas, and benign breast disease. Lactalbumin was present in 39 of 64 breast carcinomas of different types, including 77% (31) of infiltrating ductal carcinomas and 42% (seven) of infiltrating lobular carcinomas. It also was present in 55% (nine) of metastatic breast carcinomas and in 100% (five) of fibroadenomas. Lactalbumin was not observed in normal tissues and malignant neoplasms of other tissues, indicating that lactalbumin can serve as a specific tissue marker for malignant neoplasms of the breast and their metastases.