How Is Breast Cancer Related to Axillary (Underarm) Lymph Nodes?

The lymphatic system is one of the body's main tools for fighting infections. It contains lymph fluid and the lymph nodes located in critical areas of the body. Cancer cells can sometimes enter the lymphatic system and accumulate there.

Lymph nodes are small structures inside the body connected to a network of lymph vessels. They filter lymph fluid and also detect chemical changes that signal an infection. The lymph nodes in the armpit are also called axillary lymph nodes.

Axillary lymph nodes are located near both breasts. This means that if breast cancer spreads beyond breast tissue, the axillary lymph nodes are usually the first places it reaches. A person generally has 20 – 30 axillary lymph nodes, although this number varies from person to person.

Breast cancer is generally followed by a check for spread to the axillary lymph nodes as part of our work as doctors. This check helps determine the cancer diagnosis and stage.

What Is the Connection Between Breast Cancer and Axillary Lymph Nodes?

A person's cancer can metastasize (spread) to other parts of the body. Cancer spreads when some cells break away from the tumor and migrate to other parts of the body. Cancer cells can travel through the bloodstream and lymphatic system. Cells traveling through the lymphatic system can stop inside lymph nodes and grow there.

Axillary lymph nodes are in the armpits, near both breasts. Because these nodes are very close to the breast, breast cancer usually spreads to them first, before other lymph nodes.

If cancer has spread to the axillary lymph nodes, we may recommend removing all or some of the lymph nodes during a mastectomy (surgical removal of part or all of the breast).

Lymph nodes drain lymph fluid, and their removal can naturally cause some side effects after surgery. One possible side effect is lymphedema, a chronic and potentially increasing swelling of the arms.

What Are the Signs of Cancer Spreading to One or More Axillary Lymph Nodes?

General symptoms of metastatic cancer include:

• Loss of energy
• Fatigue and weakness
• Unintentional weight loss
• Pain
• Shortness of breath and difficulty breathing

Signs of breast cancer spreading to axillary lymph nodes include:

• A lump or swelling in the armpit
• Swelling in the arms or hands
• A lump or swelling in the chest and collarbone

How Is It Diagnosed?

To check whether breast cancer has spread to the axillary lymph nodes, we may recommend a physical examination and oncological imaging such as ultrasound, MRG (magnetic resonance imaging) or BT (computed tomography). During a physical examination, the specialist checks the person's armpits for swelling. If someone has been diagnosed with breast cancer, imaging called PET-BT can evaluate the underarm area very well for cancer spread.

Imaging can detect changes in the lymph nodes such as:

• Thickening of the lymph nodes
• An increase in blood vessels
• Loss of the hilum, the structure where lymph vessels leave the nodes
• Loss of the kidney-shaped appearance

According to some estimates, imaging finds cancerous nodes in one in every three women whose physical examination was considered negative. This indicates that the underarm area in people diagnosed with breast cancer should be thoroughly examined with radiological imaging.

We use several diagnostic methods to clarify whether cancer has spread to the axillary lymph nodes.

Sentinel Node Biopsy

A sentinel (guard) node biopsy involves injecting a radioactive substance or dye into the breast. The dye travels to certain lymph nodes before reaching others. Imaging is then used to identify the sentinel (guard) lymph nodes, the first nodes reached by the dye.

An interventional radiologist or general surgeon then takes tissue samples from one or more sentinel lymph nodes and sends them to a pathologist for examination. This method can help people avoid the side effects of having multiple axillary lymph nodes removed. If the pathologist finds cancer in the sentinel nodes, the person may need to have more lymph nodes removed. 

Axillary Dissection

Axillary dissection is a surgical procedure that involves removing additional lymph nodes from the armpit. Its purpose is to check whether cancer has spread and reduce the risk of cancer developing again in the lymph nodes.

In this situation, breast surgeons remove the fatty area containing most or all of the lymph nodes. The number removed varies but is generally between 5 – 30. Once the surgeon removes the nodes, the pathologist can determine whether cancer has spread beyond the sentinel lymph nodes.

Breast Cancer Staging

Cancer stage describes the extent and spread of the disease. Knowing the stage can give doctors an overall view of a person's disease and help with treatment planning.

Specialists use the tumor, node and metastasis (TNM) system to determine breast cancer stage:

• Tumor stage (T) describes the size of the initial tumor.
• Node stage (N) indicates whether breast cancer has reached the lymph nodes and how many nodes show signs of cancer cells. Node staging has subcategories to provide more specific details:

• NX: There is no information about nearby lymph nodes, or the axillary lymph nodes cannot be assessed.
• NO: Cancer has not spread to the lymph nodes.
• N1: Micrometastases or cancer cells are present in 1 – 3 axillary lymph nodes. Micrometastasis is a microscopic amount of cancer cells that can be seen during a detailed examination of the lymph nodes by a pathologist.
• N2: Cancer cells are present in 4 – 9 lymph nodes at this stage. We also use this stage to indicate that cancer has spread to lymph nodes on the inner side of the breast. These are also known as internal mammarian lymph nodes.
• N3: This stage can include a range of general findings such as:
  • Cancer is present in 10 or more axillary lymph nodes.
  • Cancer is in the lymph nodes below the collarbone.
  • Cancer is in the internal mammarian lymph nodes and in one or more axillary lymph nodes.
  • 4 or more axillary nodes are cancerous, and the internal mammarian lymph nodes have micrometastases.
  • Cancer is present in cancerous lymph nodes above the collarbone.

• Metastasis stage (M) indicates whether cancer has spread from its original site to other parts of the body.

The axillary lymph node stage is higher the more lymph nodes the cancer has spread to. Cancer stage increases according to how many different types of nodes it affects.

The 5-year survival rate is a person's probability of being alive within 5 years after diagnosis. According to the American Cancer Society, the 5-year survival rate for breast cancer that has spread to nearby lymph nodes is 86%. However, if breast cancer has spread to other parts of the body, this rate falls to 30%.

Summary

Cancer cells can leave the breast and travel around the body through the lymphatic system. This can result in cancer cells accumulating in the axillary lymph nodes. When this happens, a person may notice a lump or swelling in the armpit, near the breastbone or above/below the collarbone.

Anyone experiencing signs of breast cancer that has spread to axillary lymph nodes should consult a doctor. Early diagnosis can make cancer treatment much easier.