The lymph nodes in the armpit (axilla) drain lymph fluid from nearby areas, including the breast.
The lymph nodes in the armpit are often the first place that cancer cells spread to outside the breast. About one in three women with breast cancer have cancer cells in the lymph nodes in their armpit when their breast cancer is diagnosed.
If there are cancer cells in the lymph nodes in the armpit, it may be possible to feel a lump in the armpit. However, many women are not aware of any changes. Cancer cells in the lymph nodes can usually only be seen under a microscope and cannot be felt or seen on X-rays or scans.
Lymph nodes can become enlarged for many reasons, including having a cold or an infection. If there is a lump in the armpit, this does not necessarily mean that cancer has spread to the armpit.