What is Triple Negative Breast Cancer?

Breast cancer is not one disease. Rather, it is a group of many different diseases each defined by combinations of receptors. Receptors receive signals from the body that instruct cells to carry out specific actions. The cells of the normal breast respond to the female hormones estrogen and progesterone and these hormones instruct the breast cells to make milk, for example, in the setting of pregnancy. When breast cancers develop, many times the cancer cells retain these estrogen and progesterone receptors. About one third of the time, however, breast cancers develop and have lost these receptors (estrogen receptor (ER) negative and progesterone receptor (PR) negative). HER2 is another receptor present in the normal breast, but in approximately 25% of breast cancers it is present in excess amounts (HER2 positive).

Triple negative breast cancer is a subtype of breast cancer that lacks these three important receptors that are used as targets for cancer treatment. These receptors are important because they reveal where the cancer is most vulnerable and help determine how to best treat it. Since triple negative breast cancers lack the presence of all three of these receptors, this subtype of breast cancer is more difficult to treat and more likely to recur.

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