ABSTRACT
The most extensively used approach to identify potentially hormone-responsive breast cancers is to measure soluble estrogen receptor (ER) proteins in the supernatant, the so-called cytosol fraction of the tumor tissue homogenates, using a dextran-coated charcoal or a sucrose density gradient technique. The urgent need for a practical histochemical technique which can be used to distinguish between ER-negative and ER-positive cancers was quickly recognized by the pathologists as soon as the technology of the ER protein assays extended beyond the boundaries of the few large, federally funded biochemical laboratories. One important application of the histochemical technique is to use it as a means to identify potentially hormone-responsive breast cancers. A histochemical technique can provide a means to evaluate a function of a specific cell type, for example, the infiltrating cancer cells, using the number of cancer cells under observation as the common denominator.
