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Breast cancer cells

It is well known that the main risk factors for breast cancer are being female and being older (commonly in menopause). It means just being a woman is the biggest risk factor for developing breast cancer.

Breast cancer is the second common cancer among women (first is skin cancer) – it is the second leading cause of cancer death in women, after lung cancer.

Scientists noted that at least one in eight women will develop invasive breast cancer during their lifetime (about 12% of women). Most women who get breast cancer are over 50, but younger women can also get breast cancer. If it is discovered at early stages and if it is treated early enough, breast cancer can be cured and prevented from spreading to other parts of the body.

Nowadays breast cancer treatment protocols are pretty successful – survival rates are growing every year. To estimate and make prognosis for each case of breast cancer doctors needs to know not only tumor sizes but also breast cancer cells’ types. Depending on breast cancer cells all treatment strategies could be developed and future survival prognosis can be estimated.

Breast cancer cells

Normal healthy breast cells usually contain receptors (proteins) that attach to female hormones (estrogen and progesterone). Sometimes these hormones fuel the growth of breast cancer cells. In cases of breast cancer, cells could contain different types of receptors which can attach different substances (hormones or other proteins).

Breast cancer cells are classified as the following:

  • Cells with hormone receptors (estrogen or progesterone receptors) – so called hormone-sensitive cells (ER-positive, PR-positive).
  • Cells with positive specific HER2 receptors (HER2-positive).
  • Cells with triple positive receptors (positive for estrogen receptors, progesterone receptors, and HER2).
  • Cells with triple negative receptors (not positive for estrogen receptors, progesterone receptors and HER2).

Above mentioned breast cancer cells’ types are very important for selection of chemotherapy and for future treatments (after surgery and radiation).

Hormone-sensitive breast cancer cells

According to medical studies, about 80% of all breast cancers are ER-positive which means cancer cells grow in response to the female hormone estrogen. About 65% of breast cancer cases are PR-positive which means cells grow in response to other female hormone progesterone. These types of breast cancer called hormone-sensitive – considered hormone-receptor positive.

Good news is that tumors with ER/PR-positive are much more likely to respond to hormone therapy and treatment protocols after surgery-chemotherapy-radiation can be pretty successful. Long-term (5-10 years) hormone therapy can help prevent a return of the disease in several ways. For example, tamoxifen (Nolvadex) helps stop cancer from coming back by blocking hormone receptors, preventing hormones from binding to them. Another medication anastrozole (Arimidex), exemestane (Aromasin) and letrozole (Femara) – so called aromatase inhibitors actually stops estrogen production. These medications are only used in women who have already gone through menopause.

If the breast cancer cells don’t have either estrogen or progesterone receptors, they are called “hormone receptor-negative”.

HER2-Positive Breast Cancer

According to recent studies, in about 20% of all breast cancer cases, tumor cells make too much of specific protein known as HER2 – cancer cells that have too many copies of the HER2 gene produce too much of the growth-promoting protein called HER2. These types of breast cancer called HER2-positive and tend to be aggressive fast growing. HER2-positive breast cancer is usually treated with drugs that target HER2.

Medication trastuzumab (Herceptin) has been shown to dramatically reduce the risk of HER2-positive breast cancer coming back (along with chemotherapy after surgery and radiation).

Another medication lapatinib (Tykerb) is often given if trastuzumab doesn’t help. Ado-trastuzumab emtansine (Kadcyla) can be given after trastuzumab and a class of chemotherapy drugs called taxanes, which are commonly used to treat breast cancer. Pertuzumab (Perjeta) can be used with trastuzumab and other chemotherapy medicines to treat advanced breast cancer. This combination can also be given before surgery to treat early breast cancer.

HER2 negative breast cancer cells don’t have excess HER2. This type of breast cancer doesn’t respond to treatment with drugs that target HER2.

Triple-Negative Breast Cancer

About 10-20% of breast cancer cases are triple-negative which means that the three most common types of receptors known to fuel most breast cancer growth (estrogen, progesterone, HER-2) are not present in the cancer cells. Since the tumor cells lack the necessary receptors, common treatments like hormone therapy and drugs that target estrogen, progesterone and HER-2 are ineffective. Triple negative breast cancer can be more aggressive and difficult to treat. Also, this type is more likely to spread and recur. Using chemotherapy (before or after surgery) to treat triple negative breast cancer is still an effective option. In fact, triple negative breast cancer may respond even better to chemotherapy in the earlier stages than many other forms of cancer.

Triple negative breast cancer is more likely to affect younger people, African Americans and Hispanics. Most breast cancers associated with the gene BRCA1 are triple negative.

Triple-Positive Breast Cancer

Sometimes breast cancer could be triple-positive which means cells are ER-positive (have estrogen receptors), PR-positive (have progesterone receptors) and have too much HER2.
These cancers can be treated with hormone drugs as well as drugs that target HER2.


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