Lymphatic System

Lymphatic Vessels
These vessels lay just below the surface of the skin, and may be a structure similar to a blood vessel (vein or artery) or may merely be the space between body cells. Lymphatic Vessels are all over our body, but they may be more concentrated in certain areas. The breasts contain a greater concentration of lymphatic vessels than any other part of the body. The image only shows a sample of what one might expect to find in just one breast. The vessels continue under the areola, but for the sake of clarity they were not drawn.

Lymph Nodes or Glands (Subclavian, Interpectoral, Axillary, Parasternal, etc.)
Lymph Nodes gather the lymphatic fluid (and the debris that the fluid may be carrying from the body cells) and process it, sending any debris or waste products out of the body, if possible. When an infection "down line" from a node occurs, the node will often feel swollen. This is evidence that they are doing what they are intended to do. The Axillary nodes in particular are the ones that may be partially removed surgically and evaluated to determine if a mass in the breast might be malignant, and has become metastatic (started to spread to other parts of the body). Lymph nodes may be from the size of the head of a pin to the size of a lima bean.