Of all the skin cancers, malignant melanoma is the most serious. It accounts for approximately 75% of all skin cancer deaths and is the sixth most common form of cancer. This can be directly attributed to the fact that melanoma, unless treated early, usually metastasises to other organs.

The first place melanoma traditionally metastasises to are the lymph nodes near the site of the skin cancer. The lymph nodes are part of the lymphatic system and play an important role in immune system function. Special white blood cells called lymphocytes circulate in the body seeking out foreign cells. They return to the nodes where the foreign bodies are identified and the cells are specialised to fight that particular infection. From the node, they flow back into the blood stream, following it to the foreign cells, which they then attack.

When an infection is present, lymph nodes are commonly swollen. This is due to the large amounts of B cells, the specialised lymphocytes responsible for creating antibodies. When cancer is present, the nodes usually become enlarged and may appear as a hard knot. However, if there are only a few cancer cells, this is not always the case. If melanoma metastasises to the lymph nodes found in the chest or abdomen, patients may experience shortness of breath or backache.

Malignant melanoma may also spread to the liver, brain, lungs, or digestive tract. Cases of advanced ocular melanoma, or melanoma of the eye, metastasise to the liver in 95% of cases. In some cases, there are no symptoms of hepatic melanoma. Those that do experience symptoms may have nausea, weight loss, fever, jaundice, sweats or pain in the upper right area of the abdomen.

Approximately half of malignant melanoma tumors metastasise to the brain. Seizures are the most common symptom, appearing in 25 to 37% of patients. Symptoms can vary depending on where the tumors appear in the brain. However, in cases of metastatic brain cancer, some are more common. These include headaches, bleeding, nausea, vomiting, swelling, and impairment of motor or mental function. If sensory organs in the brain are involved, patients may have problems with hearing or vision as well.

Melanoma of the lung is rare. According to statistics, it is responsible for less than one percent of tumors in the lungs. There aren't always symptoms of this condition. Some people do experience a cough that does not respond to usual treatment, shortness of breath or fluid buildup that leads to pleural effusion (collection of fluid next to the lung). If pleural effusion is present, patients may have discomfort in the chest.

In the digestive tract, melanoma is often misdiagnosed due to its tendency to mimic the appearance of other more common disorders. Symptoms are not always present, but may include difficulty swallowing, a full sensation in the abdomen, blockage of the digestive tract or pain in the abdominal area.

With malignant melanoma, preventing metastases is critical. Once tumors metastasise, they can have devastating effects on the body. In some cases, death may result.

Everyone should know the ABCD's of melanoma; A for Asymmetry, B for Border, C for Colour and D for Diameter.  If melanoma is suspected, it should be checked immediately. Early detection increases the chances of survival from what can otherwise a fatal disease.