estrogen receptor assay

estrogen receptor assay

Oncology The ER is a protein found in high concentrations in the cytoplasm of breast, uterus, hypothalamus, and anterior hypophysis cells; ER levels are measured to determine a breast CA's potential for response to hormonal manipulation–60% of breast CAs are 'estrogen positive';12 of ER-positive Pts respond favorably to anti-estrogen–tamoxifen citrate therapy, in contrast to <13 of ER-negative Pts. See 'Flare' phenomenon. Cf Progesterone receptor assay.