Estrophilin assays in breast cancer: quantitative features and application to the mastectomy specimen.

Knowledge of the tumor content of estrogen receptor, called estrophilin, has proved to be of significant clinical value in human breast cancer. Although most breast cancer tissues contain cytosol estrophilin, essentially only patients whose cancers have moderate to high levels of estrophilin, designated estrophilin-rich, are found to respond to endocrine therapy. About two-thirds of patients with estrophilin-rich cancers obtain objective benefit from endocrine therapy. Present results indicate that predictions of response to endocrine therapy at time of recurrence can be based on the estrophilin assay of the primary lesion. Nonetheless, changes in estrophilin content during the course of disease are not uncommon. Despite an occasional patient in whom multiple samples separated by a long time have unchanged estrophilin content, there is a general tendency toward decreased estrophilin content with time.