Transferrin receptor expression in non-malignant and malignant human breast tissue.

The expression of transferrin receptor by normal, pregnant and benign hyperplastic breast lesions and by breast carcinomas has been investigated immunohistochemically using two monoclonal antibodies directed against the receptor. Unlike a previous immunohistological study in which staining was confined to malignant breast, transferrin receptor has been detected in pregnant breast and in benign lesions as well as in all carcinomas examined. The latter showed variable reactivity but with staining of most cells in 70 per cent of cases. Although the expression of transferrin receptor in non-malignant conditions may be related to cell proliferation, as has been suggested from studies of activated cells, the extent of reactivity of carcinomas has shown no correlation with tumour characteristics such as differentiation and local tumour spread. It is therefore suggested that the immunologically active transferrin receptor of breast carcinomas may have significance other than that relating to proliferation. The finding that with some carcinomas differences in staining occurred between the two antibodies is a further illustration of the complexities of the nature of transferrin receptor.