Cytochemical study of estrogen receptor in human mammary cancer.

A 17beta-estradiol-6-carboxymethyl-oxime-bovine serum albumin--fluorescein isothiocyanate conjugate is prepared by attaching on the average 11 moles of the fluorescein dye and 24 moles of the steroid hormone to each mole of the protein carrier. This fluorescent estradiol conjugate is used as a tracer to detect estrogen receptor of human mammary cancer cells in frozen sections. The cytochemical findings indicate that mammary carcinomas are composed of heterogeneous populations of receptor-positive and receptor-negative cancer cells in varying proportions and probably should be classified according to the percentages of receptor-positive cells in the cancer cell populations for better correlation with endocrine therapies.