Melanoma is a type of skin cancer, which arises from the pigment cells (melanocytes) in the skin. In a melanoma skin cancer the melanocytes become malignant and multiply excessively. One of the most important causes of melanoma is exposure to too much ultraviolet light in sunlight. The use of artificial sources of ultraviolet light, such as sunbeds, also increases the risk of getting a melanoma.
Melanocytes make a brown/black pigment (known as melanin), and often the first sign of a melanoma developing is a previous mole changing in colour or a new brown/black lesion developing. Most frequently there is darkening in colour but occasionally there is loss of pigmentation with pale areas or red areas developing. This melanoma on the skin is known as the primary melanoma.
In around 20% of patients diagnosed with melanoma, the melanoma spreads to the lymph nodes. This is classed as stage 3 melanoma.
Lymph nodes, or lymph glands, are found in our lymphatic system which is part of the body’s immune system. The (skin) lymphatics are tiny channels in the skin, which move lymph fluid around the body to the lymph nodes in the groin, under the arms (arm pits) and in the neck. As part of the immune system, the lymph fluid can carry bacteria and even cancer cells with it. Once contained within the lymph nodes, the immune system attempts to destroy them. If the immune system fails to destroy such cancer cells they can grow within the lymph nodes creating a lump. However, the lymph nodes can also swell for other reasons such as infection (e.g. when we have a sore throat there may be swollen glands in the neck).