Estrogen and progesterone are 2 female hormones. They can stimulate the growth of some cells, including breast cancer cells. Estrogen and progesterone receptors are inside (in the nucleus or other parts of the cell) or on the surface of normal breast cells and some types of breast cancer cells. These receptors are where the hormones attach to the cells. Once they are attached, the hormones can affect the behaviour or growth of the cells.
Why hormone receptor status testing is done
Knowing the hormone receptor status of the tumour helps doctors predict:
- how well the breast cancer is likely to respond to hormonal therapy
- how the tumour may behave
- what other treatments may be effective
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How hormone receptor status testing is done
The pathologist (a doctor who specializes in the causes and nature of disease) tests the breast tumour tissue to check for hormone receptors. The pathologist reports if estrogen receptors (ER) and progesterone receptors (PR) are present in the tumour cells. Based on this, the tumour is said to be:
- ER positive (ER+) or ER negative (ER–)
- PR positive (PR+) or PR negative (PR–)
In about two-thirds of all cases of breast cancer, estrogen promotes the growth of cancer because the tumour contains receptors for estrogen, progesterone or both.
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What the results mean
Knowing the hormone receptor status helps doctors decide if hormonal therapy is a treatment option.
- ER-positive tumours are more likely to respond to hormonal therapy.
- Women with PR-positive tumours may also be treated with hormonal therapy.
- If the tumour is both ER positive and PR positive (rather than only ER positive), it may better respond to hormonal therapy.
- Tumours that are hormone receptor negative (ER– and PR–) are not likely to respond to hormonal therapy.
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Hormone receptor status at recurrence
Sometimes breast cancer may come back (recur) after it has been treated. A biopsy of tissue from a tumour may be done to confirm the diagnosis of breast cancer recurrence (local recurrence) or to rule out a new primary breast cancer. Hormone receptor status may be re-checked at this time.
- Women whose first tumours were ER positive may develop ER-negative tumours at the time of recurrence. This is an important prognostic factor because the tumour may respond poorly to additional hormonal therapy.
- The cancer may respond to hormonal therapy if a recurrence occurs several years after the first diagnosis of breast cancer and the first tumour was hormone receptor negative.
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