Definition and Overview
Malignant melanoma is a life-threatening skin cancer. It is much less common than other types of skin cancer (squamous and basal cell skin cancers) but it is the most serious type.
Melanoma develops in melanin-forming cells (melanocytes) found between the dermis and epidermis. It is very aggressive and is likely to spread to other parts of the body unless treated quickly. It is a good thing that melanomas are easily spotted because they cause abnormal changes in the skin. They are often black and brown in colour but can also show other shades. Most melanomas develop in the chest, face, neck, legs, and back. Sometimes, however, they form in the genitals, anal area, eyes, and mouth.
Although it can affect individuals of any racial or ethnic group, melanoma is more prevalent among white-skinned Caucasians who are 26 times more likely to develop the condition than African-Americans. The highest incidence of melanoma has been recorded in Australia and New Zealand. Researchers believe that this is due to the countries’ proximity to the equator and their greatly reduced ozone layer.
In the US and Canada, the condition affects up to 50 per 100,000 people per year. The annual increase in incidence rate is between 3% and 7% but mortality rates are slowly decreasing.
Because melanomas develop where they can be easily seen, patients are often the first to notice them. This is important as early detection and diagnosis are crucial to improve patient’s prognosis. When caught early, the condition can be treated with a simple outpatient procedure.
Causes of the Condition
A huge number of malignant melanoma cases are caused by too much exposure to the sun's ultraviolent rays (UV). There are two types of UV rays: short wave ultraviolet B (UVB) and long wave ultraviolet A (UVA). Both contribute to skin ageing and wrinkling but UVB, which is stronger than UVA rays, is more intense and the most common cause of sunburn. A blistering sunburn during childhood increases one’s risk of developing skin cancer later in life.
As with all cancers, researchers are still in the process of establishing the definitive cause of invasive malignant melanoma. However, they have already successfully confirmed a link between melanoma and various risk factors, including heredity. One in every ten patients diagnosed with the condition has a family member with a history of the disease.
Patients who have a history of other sun-induced skin cancers such as squamous cell carcinomas and common basal cell also have an increased risk of developing both malignant and non-malignant melanoma (non-cancerous).
Melanoma, unlike other types of cancer, produces hard-to-ignore symptoms that allow for early detection and diagnosis. This is crucial as the disease can be cured if caught right away or when the malignant tumour is confined to the epidermis (malignant melanoma in situ). The tumour can be removed with a simple excision procedure performed under local anaesthesia.
One of the most common malignant melanoma symptoms is the presence of a new spot on the skin that changes in colour, shape, and size. It is typically asymmetrical with irregular edges, has different shades of brown or black, and larger than 6 millimeters across. Some patients develop a sore that does not heal and is tender to touch, painful, or itchy or a red lump that appears crusty, dry, or scaly.
Who to See and Types of Treatments Available
Patients with symptoms of malignant melanoma must consult a dermatologist for diagnosis and treatment right away. Malignant melanoma is diagnosed with a skin exam and a biopsy in which a sample of the abnormal tissue is obtained and tested under a microscope to check for cancer cells. If cancer has been confirmed, the next step is staging to determine the extent of the condition and if cancer cells have already spread to other parts of the body. Such information is used to determine the best treatment for malignant melanoma.
Malignant melanoma stages and corresponding treatment:
- Stage 0 (malignant melanoma in situ) - Abnormal melanocytes are found only in the epidermis.
Treatment: Malignant melanoma in situ is treated by excising the abnormal growth along with 0.5 centimeters of normal-looking skin surrounding it. This is a preventive measure to ensure that no cancer cells remain in the area. The procedure is outpatient and is performed under local anaesthesia. The survival rate for Stage 0 malignant melanoma is between 99% and 100%.
Stage I – Cancer has formed and there’s a tumour measuring more than 1 millimeter thick (with or without ulceration).
Stage II – The malignant tumour is between one and four millimeters thick (with or without ulceration).
Treatment: Malignant melanoma treatment for stages I and II involves the surgical excision of melanoma and lymph node dissection with or without adjuvant therapy (chemotherapy or radiation therapy) to kill remaining cancer cells.
- Stage III – Cancer has spread to the lymph nodes.
Treatment: Wide excision of the primary tumour and lymph node dissection followed by adjuvant therapy, which could be immunotherapy, targeted therapy, chemotherapy, or a combination of immunotherapy and chemotherapy.
- Stage IV – Cancer has spread to other parts of the body, which may include the liver, lungs, brain, soft tissue, bone, or gastrointestinal tract.
Treatment: Stage IV melanoma, also known as metastatic malignant melanoma, is often hard to cure as cancer cells have already invaded even distant body parts. Depending on the age and the patient’s overall health condition, doctors may recommend surgery to remove metastases in internal organs. If surgery cannot be performed, targeted therapy, immunotherapy, radiation therapy, or chemotherapy will be suggested. Malignant melanoma prognosis for patients with stage 4 of the disease is generally poor with a five-year survival rate of about 15-20%.
Melanoma. (2014). National Cancer Institute. https://www.cancer.gov/types/skin
Stages of melanoma. https://www.cancer.gov/types/skin/patient/melanoma-treatment-pdq#link/_96 Survival rates for melanoma skin cancer, by stage (http://www.cancer.org/cancer/skincancer-melanoma/detailedguide/melanoma-skin-cancer-survival-rates-by-stage