What is breast cancer?

Breast cancer is a malignant tumor in the breast that mainly affects women. How the disease develops depends on various factors. Breast cancer treatment can be highly effective, particularly when the disease is identified early. On this page, you can learn more about the different types, symptoms, diagnosis, risk factors and prevention, as well as treatment options.

31 March 2022

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In Switzerland, around 6,300 women and 50 men are diagnosed with breast cancer, a malignant tumor in the breast, every year. Breast cancer is the most common type of cancer in women and accounts for almost one third of all cancer diagnoses. The rate of disease increases with age. Nevertheless, a quarter of all patients are younger than 50 at the time of diagnosis. Worldwide, breast cancer is the most common cancer diagnosed, affecting more than 2.3 million people. The pink ribbon is an unmistakable symbol of solidarity and commitment in the fight against breast cancer. Because early detection of this cancer is particularly important for the chances of cure.

Types of breast cancer

There are many different types of breast cancer. Most breast cancers are carcinomas. These are tumors that develop in the epithelial cells that line organs and tissues throughout the body. In medicine, breast cancer is called mammary carcinoma (from Latin mamma “breast, female mammary gland”).

Ductal breast carcinoma

  • starts mainly in the cells of the milk ducts
  • is the most common type of breast cancer, accounting for about 50-80% of all cases.

Lobular breast carcinoma

  • arises in the milk-producing glands (lobules)
  • accounts for 5-15% of breast cancers.

In-situ or invasive breast cancer

The type of breast cancer can also be distinguished by whether or not the tumor has spread or not.

  • In-situ breast cancer: is a pre-cancer. It is confined to its site of origin and has not yet spread to the surrounding breast tissue.
  • Invasive breast cancer: the tumor has already spread into surrounding breast tissue. There is a risk of metastases spreading to other tissues and organs.

Receptor status of breast cancer

In breast cancer, the receptor status is also taken into account. It tells whether the tumor is hormone-sensitive and how fast it grows.

HR status means hormone receptor status. It indicates whether a tumor has binding sites for the hormones estrogen and/or progesterone. If the cancer cell has one or both of the receptors, it is called hormone receptor positive or HR+).

HER2 is a protein that helps breast cancer cells grow quickly. Breast cancer cells with higher than normal levels of HER2 are called HER2-positive.

Ki-67 is a protein in cells that increases as they prepare to divide into new cells. The so-called Ki-67 proliferation index indicates how fast a tumor grows.   

HR-positive/HER2-negative breast cancer
This is the most common type of breast cancer by receptor status, accounting for approximately 70%.Tumor cells have hormone-binding sites but not increased levels of growth factor receptors.

Triple-negative breast cancer (TNBC)
TNBC is an aggressive form of breast cancer that  accounts for about 10-15%  of all breast cancers. The term “triple-negative” refers to the fact that the cancer cells don’t have estrogen or progesterone receptors and do not produce an increased amount  of HER2. TNBC often affects younger women.

There are other types of breast cancers that start to grow in other types of cells in the breast and are much less common.

Stetoscope and pink ribbon on the table

Symptoms of breast cancer

Breast cancer is often not discovered until the tumor is large enough to palpate. Often, those affected do not experience any symptoms until that time.

Possible signs of breast cancer:

  • painless lump or hardened area in the breast
  • sudden inflammation or redness of the breast
  • sudden dimpling or bulging of the skin, especially in the nipple area
  • the nipple is inflamed
  • the breast suddenly becomes larger
  • a nipple discharge other than breast milk
  • swollen lymph nodes in the armpit and below and above the collarbone
  • unintentional weight loss


Breast cancer can be detected by mammography, an X-ray examination of the breast. The definitive diagnosis is made by means of biopsy, the removal of a tissue sample.

Risk factors

Possible risk factors for breast cancer include:

  • Gender: being a woman is the biggest risk factor for developing breast cancer
  • Age: older women are more likely to develop the disease than younger women
  • Family history: if family members have breast cancer, the risk of disease increases
  • Genetics: if gene mutations are present
  • Hormonal factors: e.g. first menstruation before the age of 12, last menstruation after the age of 55; birth of the first child after the age of 30 or many years of combined hormone therapy for menopausal symptoms
  • Radiation therapy: e.g., if the upper body has been irradiated for another cancer
  • Obesity, alcohol and smoking.

Prevention and early detection

In addition to the preventive checkup at the gynecologist, every woman should palpate her breast regularly to notice changes.

For women over 50, mammography is recommended to detect breast cancer at an early stage.

Breast cancer treatment

Today, significantly fewer women die from breast cancer than twenty years ago. This is due to improved early detection and new and more advanced therapies. Treatment options include surgery, chemotherapies, radiotherapies, anti-hormone therapies, immunotherapies and targeted therapies. Often, different types of therapy are combined.

The earlier breast cancer is detected and treated, the better the chances of cure.

CH-NON-01561, 02/2022