estrogen receptor (ER)


A protein in some healthy and cancerous (malignant) cells that binds with estrogen.

An estrogen receptor assay (test) is used to find out if breast cancer cells have estrogen receptors, which will help doctors to decide on a treatment plan. If the cells have estrogen receptors, they are called estrogen receptor positive (ER+). If the cells don’t have estrogen receptors, they are called estrogen receptor negative (ER–).

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