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 located all over our body, but they are 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 here.

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 transport any debris or waste products into the blood stream, to be eliminated, if possible. When an infection "up the line" from a lymph node occurs, the  associated node will often be swollen and can be felt through the skin during a Breast Self Examination. This is evidence that the node is doing what it is intended to do. The Axillary nodes (in the armpit) in particular are the ones that may be partially removed surgically when cancer is found in the breast. The reason for this is that a major portion of the lymphatic circulation from the breast goes toward the upper outer quadrant of each breast and then moves back to the axillary nodes. Therefore, the thinking is that if any cells are "out and about", they will most likely go to the axillary nodes and be caught up for elimination from the body. A dozen or two of these nodes (there may be as many as 60 or more nodes in the armpit) are excised and evaluated to determine if a mass in the breast might be malignant, and the malignancy 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. If swollen, they can easily triple in size. During a Breast Self Examination the nodes should be monitored for swelling, which could indicate an infection or a malignancy in the breast and warrant further investigation.

Currently, a process called Sentinel Node Biopsy (SNB) is being used to reduce the number of lymph nodes that have to be removed during a lymph node biopsy. It is not that simple to remove a specific number of lymph nodes, due to the difficulty of finding them hidden among the fatty tissues. In a SNB, a dye is injected directly into the location of the suspicious mass in the breast, and the lymphatic vessels that are charged with the duty of cleansing that particular location will pick up that dye after a short while and take it back to their node. When the biopsy is done, the node with the dye is more likely to be identifiable, making the removal of a larger number of nodes unnecessary. The thought behind this is that when a malignancy in the breast (or any other part of the body for that matter) starts to metastasize (send off "seeds" or loose cells to start cancers elsewhere in the body) the lymphatic system will sweep them up and take them to the associated lymph node. The same thing happened to the dye that was injected. Once the associated lymph node is found, it is excised (removed surgically) and dissected under a microscope to see if it has any of those wandering malignant cells. If ANY cells have left the malignant mass, it is extremely likely that the associated lymph node will have picked some of them up. if one or more malignant cells are found, more have likely been released and chemo-therapy most likely will be prescribed. if no malignant cells are found in the "sentinel node", it is accepted that there have most likely not been any malignant cells released from the breast mass, and chemo-therapy will probably NOT be prescribed. If you are facing a lymph node dissection, I strongly suggest that you ask your surgeon about having a Sentinel Node Biopsy. The benefits of this are a much lower likelihood of developing lymphedema in the associated arm.