When breast cancer spreads, it typically first affects nearby lymph nodes, particularly those under the arm. Lymph nodes are part of the lymphatic system, which circulates lymph—a clear fluid that contains infection-fighting white blood cells—throughout the body to remove toxins, waste, and other unwanted material. If cancer cells reach the lymph nodes, there is a chance they have also spread beyond the breast.
When an oncologist performs tests and finds breast cancer cells in the lymph nodes, this is referred to as lymph node involvement. Understanding whether your lymph nodes are affected is essential for staging the cancer and determining the most effective breast cancer treatment plan for you.
How Lymph Node Involvement is Determined
To determine whether your lymph nodes are affected, the breast cancer specialist will remove one or more underarm lymph nodes for examination under a microscope.
There are two methods for checking lymph nodes: sentinel lymph node biopsy and axillary lymph node dissection. One of these approaches is often performed as part of the breast cancer removal procedure, but it can also be done as a separate procedure if necessary.
Sentinel Lymph Node Biopsy (SLNB)
A sentinel lymph node is the first lymph node where cancer cells are most likely to spread to from a primary tumor. Sometimes, multiple sentinel lymph nodes may be present.
During surgery to remove breast cancer, the sentinel node is identified and removed. This node is sent to a pathologist — a specialist who examines tissues and diagnoses diseases — to check for cancer cells. It is the most common and least invasive method for checking lymph nodes.
To locate the sentinel node, the surgeon injects a radioactive substance or blue dye near the tumor, which travels through the lymph vessels. The first lymph node (or nodes) the dye or radioactive substance reaches will be the sentinel node. The surgeon makes a small incision and removes the node for testing.
The pathology results help determine the stage of breast cancer and plan treatment. If the sentinel node shows no signs of cancer (lymph node-negative), it is unlikely that other lymph nodes have cancer, and additional nodes may not need to be removed. However, if breast cancer is present in the sentinel nodes (lymph node-positive), more lymph nodes may need to be removed through a procedure called axillary dissection.
Axillary Lymph Node Dissection (ALND)
Axillary lymph nodes are located from your breast tissue into the armpit. This area under the arm is called the axilla.
During an axillary lymph node dissection, anywhere from 10 to 40 lymph nodes are removed and examined by a pathologist. These nodes are typically removed during either a lumpectomy or a mastectomy. Because the removal of this many lymph nodes can result in poor lymph fluid drainage in the arm, it’s used less frequently.
Lymph Node Involvement Influences Treatment Options
The lymph nodes are then tested by the pathologist, who produces a report detailing the results. This pathology report includes the number of lymph nodes removed during the procedure and shows how many were "involved" or tested positive for cancer. This is known as lymph node status.
Node-negative status means the breast cancer has not spread to nearby lymph nodes. Node-positive status indicates that cancer is found in the lymph nodes, suggesting that it may have already spread or could spread to other organs, including the bones, liver, lungs, and brain. Additional tests are necessary to confirm this.
The report also describes the extent of cancer in each lymph node. Cancer cells can vary in size and number. This information may be reported as:
- Microscopic (or minimal): This indicates that only a few cancer cells are present in the node and can only be seen under a microscope.
- Gross (significant or macroscopic): This suggests that a larger amount of cancer can be seen or felt without using a microscope.
- Extracapsular extension: This means the cancer has spread (metastasized) outside the wall of the lymph node.
If cancer is found in the lymph nodes, your oncologist will likely recommend systemic treatments along with surgery. These drugs move throughout the body, including the lymph nodes, to kill cancer cells. Systemic treatments include chemotherapy, targeted therapy, hormone therapy, and immunotherapy.
Breast Cancer Treatment in the Willamette Valley
If you or a loved one receives a breast cancer diagnosis, it is important to consult with a breast cancer oncologist and surgeon who specializes in breast cancer. Together, our physicians will create a plan for removing the cancer, understanding whether lymph nodes are involved, and treatment that will reduce the likelihood of recurrence. Our breast cancer doctors are available for consultation at a location convenient to you in Albany, Corvallis, Eugene, Florence, Lincoln City, Newport, and Springfield, Oregon.
