Patterns of reaction of monoclonal antibodies HMFG-1 and -2 with benign breast tissues and breast carcinomas.

The monoclonal antibodies HMFG-1 and HMFG-2 are directed against different epitopes on a large molecule in the human milk fat globule and are also expressed on breast tumors. Here we examine the relative intensity of staining of the two antibodies in formalin fixed paraffin embedded tissue sections from malignant and benign mammary lesions. Most ductal carcinomas and their lymph node metastases stained more strongly with HMFG-2 whereas primary lobular carcinomas are more variable but the majority of their lymph node metastases stained more strongly with HMFG-1. Western blots of gel separated extracts of formalin fixed, paraffin embedded tumor tissue, stained with the antibodies in an ELISA assay, show that the molecular weight of components expressing the antigenic determinants varies. Smaller molecular weight components recognised by HMFG-2 and present in metastatic tumors may be lost during tissue processing. To assess the importance of the molecular weight parameter in tumor classification and prognosis it will be necessary to use frozen tissue.