How Melanoma Spreads to the Lymph Nodes
Most primary melanomas will grow and spread horizontally along the top layer of the skin or epidermis before they begin to penetrate deeper into the layers of the dermis of the skin. When they do grow deeper into the skin, the melanoma cells can reach the lymph and blood vessels in the dermis.
Sometimes melanoma cells break away from the primary tumor and enter the lymph vessels. They may then spread along the lymph vessels, forming in-transit (satellite) metastases, and eventually spread to the regional lymph nodes.
In any area of skin where there is a deeply penetrating melanoma, there will be a nearby sentinel node (or less frequently, 2 or more nodes) to which it drains. The sentinel lymph node is the very first lymph node to receive drainage from that area. When lymph does its job to filter the skin, and drains an area of skin that contains melanoma, the sentinel lymph node is the one most likely to contain melanoma cells if any lymph nodes are involved.
Techniques are available that help doctors accurately locate sentinel lymph nodes and enable the surgeon to remove them through better-directed and smaller incisions.Learn more about sentinel lymph node biopsy
The Lymphatic System
What It Is
The lymphatic system consists of tissues and organs that produce and store lymph, and a network of vessels that carry lymph throughout the body.
Lymph is an almost colorless fluid that contains lymphocytes, white blood cells of the immune system that help fight infection and disease. Lymph bathes the cells of the body with water and nutrients, and carries away the body’s waste and foreign bodies including bacteria, viruses, and cancer cells.
Lymph also bring immune cells to areas of the body that are fighting infection. Lymph is stored in special tissues as well as transported throughout the body with water and nutrients.
Lymph nodes are bean-shaped collections of lymphatic tissue that filter lymph, trap foreign bodies (including cancer cells), and fight infection and disease. Lymph vessels then recirculate the filtered lymph throughout the body.
Lymph vessels are thin delicate vessels that run alongside our blood vessels. Like blood vessels, they go to all the tissues of the body.
Major Classes of Lymphocytes
The bone marrow, thymus, spleen, appendix, tonsils, and adenoids all produce and store lymph.
The major classes of lymphocytes are known as T cells, B cells, and Natural Killer (NK) cells:
- T cells are produced in the bone marrow and mature in the thymus.
- B cells are produced in the bone marrow and mature in the bone marrow.
The 3 Main Lymph Node Basins Are:
- The cervical basin – located beneath the jaw along the front of the neck. These are the lymph nodes that doctors often feel when someone has a sore throat. When lymph nodes are involved in fighting an infection, they become swollen and tender. When someone says they have swollen glands in their neck, they are referring to these cervical lymph nodes (which actually have no glandular tissue in them).
- The axillary basin – located beneath one’s armpits, on the side of the chest beneath the chest muscles (pectoralis major).
- The inguinal basin – located in the groin, at the crease that is formed by the hip joints, where the upper thigh meets the hip.