Breast cancer is the most common cancer in women. In rare cases, it can also occur in men. In Switzerland, around 6,500 women and 50 men are diagnosed with breast cancer every year. A quarter of those affected are under 50 years old at this time. The risk of developing the disease increases significantly from the age of 50.

Breast cancer, also known as mammary carcinoma in medicine, is a tumor disease of the breast.

What is breast cancer?

Breast cancer is a form of cancer that develops in the breast.

Breast cancer can develop when originally healthy cells in the breast begin to grow uncontrollably, divide and grow into surrounding tissue. These rapidly multiplying cells can form a tumor.

Cancer cells can spread via the lymphatic and blood vessels and form metastases (offshoots) in other parts of the body.

Types of breast cancer

There are many different types of breast cancer, which differ according to the origin of the cancer cells and the tumor characteristics.

Most breast cancers are carcinomas (tumors of the uppermost tissue layer) and originate from the cells of the milk ducts or from the cells of the mammary glands in the breast:

  • Ductal breast cancer: develops in the milk ducts.
  • Lobular breast carcinoma: develops in the mammary glands.

Depending on the spread of the cancer cells, it is referred to as in-situ breast cancer or invasive breast cancer:

  • In situ: The cancer cells are still at their place of origin.
  • Invasive: The cancer cells have already spread to neighboring breast tissue.

Breast cancer is also differentiated according to whether the cancer cells have certain receptors that influence their growth.

  • Oestrogen receptor-positive (ER+)
    The cancer cells have receptors for the hormone oestrogen. This means that the cancer is hormone-sensitive and grows in the presence of oestrogen.
  • Progesterone receptor-positive (PR+)
    The cancer cells have receptors for the hormone progesterone. The cancer is correspondingly hormone-sensitive and grows in a hormone-dependent manner.
  • HER2-positive / HER2-negative
    HER2 means human epidermal growth factor receptor. It transmits growth signals to the inside of the cancer cells.

    • HER2-positive breast cancer
      Many of these HER2 receptors are present on the cancer cells, which is why the cancer cells divide more frequently. The tumor grows faster.
    • HER2-negative breast cancer
      The cancer cells have few or no HER2 receptors and therefore do not respond to therapies that specifically target the HER2 protein.

Triple-negative breast cancer (TNBC)
TNBC is a specific form of breast cancer in which neither receptors for the hormones oestrogen and progesterone nor the growth factor receptor HER2 can be detected on the cancer cells. Therefore triple “negative”.

  • This form of breast cancer occurs more frequently in young women under the age of 40.
  • Around 15 % of all breast cancers are TNBC.

Symptoms

Breast cancer may not cause any symptoms for a long time. It is therefore important to look out for certain signs of breast cancer.

These include, among others:

  • Hardening or lump in the breast
  • Change in breast shape and size
  • Swelling or redness
  • Dents in the skin
  • Changes in the nipple
  • Swollen lymph nodes in the armpit

Important: These symptoms can also have other causes. Not every one of these signs is necessarily an indication of breast cancer. However, they should be checked by a doctor to be on the safe side.

Causes and risk factors

Why breast cancer develops has not yet been conclusively clarified. It is assumed that various factors can increase the risk of the disease.

These include, among others:

  • Severe overweight
  • Lack of exercise
  • Alcohol consumption
  • Nicotine
  • Heredity
  • Early first or late last menstruation
  • Childlessness
  • Late first pregnancy
  • Hormone therapy during the menopause

A healthy lifestyle can help to reduce the risk of breast cancer.

Treatment options

In many cases, surgery to remove the tumor is one of the treatment options. One or more other therapies may also be used.

The treatment options include:

  • Surgery: to remove the tumor tissue.
  • Radiotherapy: The cancer cells are destroyed by high-energy radiation.
  • Chemotherapies: Drugs that circulate in the bloodstream and can reach and kill rapidly growing cells, including cancer cells, throughout the body.
  • Hormone therapies: Drugs that can slow down or stop certain breast cancer cells that rely on hormones, particularly oestrogen and progesterone, to grow.
  • Targeted therapies: specifically developed drugs that can block or slow down certain mechanisms and pathways responsible for the growth, division and spread of cancer cells.
  • Immunotherapies: biotechnologically produced drugs that activate or strengthen the body’s own immune system in order to recognize and destroy cancer cells more effectively.

Which of these therapies is used depends on various factors, including the general state of health, the size, location and characteristics of the tumor and whether the patient wishes to have children. The various factors are carefully weighed up when drawing up the individual treatment plan. It is possible for therapies to be combined or applied one after the other.

CH-ONC-24-00011, 04/2024

Other treatment areas

Uterine cancer

Uterine cancer is the most common cancer of the female reproductive organs. It mainly occurs in women after the menopause.

Liver cancer

Liver cancer is a tumor disease of the liver. It mainly occurs in older people. The incidence of the disease increases with age.

Kidney Cancer

Kidney cancer, also known as renal cell carcinoma, is a cancer of the kidney. Older people around the age of 75 are affected more frequently.

Thyroid cancer

Thyroid cancer is a rare type of cancer that occurs more frequently in women than in men. It can also affect young people.

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