Binding of Lectins to Human Mammary Tumors: Ultrastructural Study

The site of several lectin receptors in human mammary tumors and stroma was studied with the electron microscope. The advantage of the ultrastructural over light microscopic study was that lectin receptors could be localized with precision on the different cell types of the tumor and stroma. Eighteen human mammary carcinomas were incubated with three peroxidase-labeled lectins: peanut agglutinin (PNA), Helix pomatia, and Ulex europaeus I (UEA). These lectins reacted in a selective way; some tumors were negative and others showed reaction in some areas of the tumor and/or the stroma. No correlation was found, however, between the presence of these lectin receptors on the tumor cells and either hormone receptors or histological type of the tumors. These results show that the value of the presence of lectin receptors in human mammary tumors as markers for evaluation of mammary lesions is more complex than thought up to now. The most relevant observations on the stroma cells and inflammatory infiltrates were: (A) Some lymphocytes were positive with PNA, probably representing sessile T cells. In two carcinomas, abundant plasma cells were present in the infiltrates, always with PNA receptors. (B) In all mammary tumors where blood vessels were present in the sections, these were always stained with UEA. This supports the use of UEA as a marker for human endothelial cells even in pathologically altered tissues.