Immunohistochemical analysis of estrogen receptors (ER) using formalin-fixed paraffin-embedded breast cancer tissue: correlation with clinical endocrine response.

A new immunohistochemical assay utilizing anti-ER monoclonal antibodies (H 222, Abbott) for detection of ER in formalin-fixed paraffin-embedded breast cancer tissue has been clinically evaluated. It is shown that tumors containing immunoreactive epithelial cells are much better candidates for hormonal manipulation than those without. In addition, primary tumors and corresponding regional lymph node metastases contain qualitatively the same ER pattern. The potentials and limitations of the present method are discussed in relation to other well-known ER assays.