Melanoma is the most lethal form of skin cancer. We as South Africans are particularly at risk because of our excellent weather and outdoor lifestyle. These cancerous growths develop when DNA damage occurs in skin cells (most often caused by ultraviolet radiation from sun exposure or tanning beds). This triggers genetic mutations that cause the skin cells to multiply rapidly and form malignant tumours. These tumours originate in the pigment-producing melanocytes in the basal layer of the epidermis (the upper layer of the skin) and mostly resemble the appearance of moles. Most melanomas are black or brown, but they can also be pink, red, purple, blue or white.
Melanoma warning signs:
You should examine your skin from head to toe at least once a month to look for any new moles or changes in existing moles. Lesions that itch, bleed or do not heal are also danger signs. The following melanoma characteristics are important to recognize when evaluating moles for the presence of melanomas (ABCDE!):
Melanomas may develop anywhere on your body but often develop in areas that have been exposed to the sun, such as your back, legs, arms and face. Melanomas may also develop in areas that are not exposed to the sun, such as the soles of your feet, the palms of your hands and fingernail beds. These are categorized as hidden melanomas and are more common in people with dark skin.
Melanomas don’t always start as a mole; they may develop on normal-looking skin.
Risk factors for developing melanoma are as follows:
If melanoma is detected and treated early, the chance of cure is excellent. If it is detected after it has spread to other organs, it can be very difficult to treat and may be fatal.
There are 4 recognized types of melanoma:
Three of them occupy the top layers of the skin and only occasionally become invasive, whereas the fourth type is invasive from the start. Invasive melanomas carry a poorer prognosis.
How are melanomas treated?
Once the diagnosis of melanoma is considered, it needs to be confirmed/excluded by performing a surgical biopsy. The lesion is excised with a 1mm margin and sent for histological evaluation. The histology will confirm the diagnosis; determine the type of melanoma and the depth of infiltration. The depth of infiltration is the most important as this will determine the prognosis to a large extent, and will also determine with what size of margin the biopsy scar needs to be re-excised. This is necessary to decrease the chance of a local recurrence:
Normally cell growth occurs via an orderly process With a sentinel lymph node biopsy, a radioactive substance is injected into the tumour site. The first lymph node that drains the area of the melanoma (i.e. a groin lymph node if the lesion is on the skin of the leg) is identified and removed. If there is cancer in this node, all the lymph nodes of the groin area are removed; if it is clear of cancer, no further surgery is done.
Patients with deep primary tumours (>4mm thick) or those with the lymph-node positive disease are considered to have a high risk of systemic/recurrent disease and would qualify for some form of adjuvant therapy such as chemotherapy, immunotherapy or radiation therapy. Interferon alfa is approved for adjuvant treatment after excision in patients who are free of disease but are at high risk for recurrence.
Conventional chemotherapy, radiotherapy, granulocyte-macrophage colony-stimulating factor (GM-CSF) and immunotherapy (vemurafenib) all have a role to play in the adjuvant setting.