The lymph (lymphatic) system of the breast

The lymph (lymphatic) system of the breast

The lymph system is important to understand because it is one way breast cancers can
spread. This system has several parts.
Lymph nodes are small, bean-shaped collections of immune system cells (cells that are
important in fighting infections) that are connected by lymphatic vessels. Lymphatic
vessels are like small veins, except that they carry a clear fluid called lymph (instead of
blood) away from the breast. Lymph contains tissue fluid and waste products, as well as
immune system cells. Breast cancer cells can enter lymphatic vessels and begin to grow
in lymph nodes.
Most lymphatic vessels in the breast connect to lymph nodes under the arm (axillary
nodes). Some lymphatic vessels connect to lymph nodes inside the chest (internal
mammary nodes) and those either above or below the collarbone (supraclavicular or
infraclavicular nodes).

If the cancer cells have spread to lymph nodes, there is a higher chance that the cells
could have also gotten into the bloodstream and spread (metastasized) to other sites in the
body. The more lymph nodes that have breast cancer, the more likely it is that the cancer
may be found in other organs as well. Because of this, finding cancer in one or more
lymph nodes often affects the treatment plan. Still, not all women with cancer cells in
their lymph nodes develop metastases, and some women can have no cancer cells in their
lymph nodes and later develop metastases.