The term melanoma translates to ‘black tumor’. It is one of the three types of cancers that begin in skin cells. Of the three types, melanoma is rarest but most dangerous. Specifically, the disease begins in cells located in the bottom layer of the epidermis. These cells are known as melanocytes and are responsible for making melanin. More melanocytes in one place result in spots or skin growths with more pigment, hence the term black tumor or melanoma. Some forms of melanoma however lack pigment and appear as pink, red or skin colored.
It is not known exactly what causes the disease. But like other cancers, changes in DNA are largely responsible. Risk factors may include;
- Having blue or green eyes
- Being fair skinned
- Weakened immunity
- History of sunburns
- Atypical nevi syndrome
- Family history of the disease
- Using tanning beds
Melanocytes occur in largest numbers throughout the skin. The cells also occur in mucosal membranes and uveal tract in eyes. This means that symptoms can be observed in any of these body areas. Some rare cases include melanoma on breast, vagina, vulva and penis.
Since cutaneous melanoma is most common, symptoms usually revolve around abnormal or irregular moles. The ABCDEs can be used to check for early suspicious signs. Normally, benign skin growths or spots will be symmetrical, have regular borders, be consistent in coloration, be less than 5mm in thickness and stay in the same state for long. The opposite is true for melanomas. There are many pictures of melanoma which can help illustrate.
Who is at risk?
Melanoma can develop in anyone. People with a history of sunburns especially during early ages are particularly at risk.
About 75% of all melanomas begin in normal skin. The rest arise on existing moles. It is for this reason that a lot of emphasis is put on using the ABCDEs for physical examination at home.
UV radiation has been identified to be the most common risk factor. It is in fact identified as one of the possible choroidal melanoma causes. While sun is the greatest source of UV radiation, artificial devices such as tanning beds also emit the radiation. It is estimated that 15 minutes tanning beds use is equivalent to a whole day of sunbathing.
Prognosis is best when melanoma is still confined to the epidermis. Survival rate is more than 90% then. This drops to 50% and below 20% for stage 3 and stage 4 respectively. See what is metastatic melanoma, to understand how the disease goes from one stage to another.
While most skin cancer cases are not caused by melanoma, most deaths are. This is very worrying, considering that cancer of the skin is the most common.
Of all skin cancer cases, melanoma is only responsible for about 4%. Interestingly, the 4% results in 80% of all skin cancer-related deaths.
Children rarely develop melanoma. UV radiation exposure during childhood years makes it more likely that the disease will show up sometimes after adolescence.
In the last century, melanoma has become very commonly diagnosed. It is estimated to have an increase rate of about 2000%. This is higher than all the other types of cancer put together.
More cases are being reported in young people, between ages of 15 and 30 years. Melanoma is set to become the second or most common form of cancer in this age group.
In men the disease mostly shows up in the neck and head areas as well as the trunk. Melanoma on back accounts for about 30% of all cases in men while head and neck areas account for about 60%. It is below age 50 that men are most likely to develop melanoma. Between 15 and 40 years, twice as many men compared to women will succumb to the disease.
In women, the disease mostly shows up on legs. It is the leading cause of cancer-related deaths in women between ages of 25 and 30. Above 30 years, melanoma is second to breast cancer in terms of cancer-related diagnoses.
Fair skinned people are more likely to develop the disease. They also are more likely to catch the disease in its earliest stages.
African Americans have more melanin on their skins. This protects them from UV radiation. The problem is that colored people are more likely to be diagnosed with advanced melanoma. It is made worse by the misguided belief that colored people don’t develop melanoma.
Doctors rely on a number of tests to confirm melanoma diagnosis. Melanoma biopsy is the most accurate. There are three types of biopsies that may be taken;
- Punch biopsy – here, a round skin tissue from a mole with signs of malignancy is removed. The tissue is taken to the lab and examined under a microscope.
- Excisional biopsy – this is the most commonly used type. The entire mole and some surrounding tissue are cut out.
- Incisional biopsy – the part of the mole showing most signs of malignancy is removed and taken to the lab for investigation.
Melanoma surgery is usually the primary treatment method. First, imaging tests will be taken to show the thickness and location of the tumor. The doctor will then draw an excision margin. The tumor along some surrounding tissue and the underneath cutaneous tissue will be removed.
For melanoma in situ, wide excision will be necessary to ensure that all malignant tissues have been removed. 5mm melanoma in situ margins are traditionally used for wide excision. Large tumors may require margins as large as 2cm. Skin grafting may be considered for cases such as melanoma on face or finger.
Surgery may also be done to completely remove entire tissues or organs. A good example is removal of lymph nodes after stage 2.
In simple terms, melanoma immunotherapy is use of substances, mainly medicines, to boost a patient’s immune system so that it can recognize and kill cancer cells. It is one of the most recent melanoma treatment options to be introduced. In most cases, this option is used to shrink tumors and stop their spread rather than completely removing them. Immunotherapy is of the following types;
Checkpoint proteins inhibitors
Immune cells recognize healthy cells by presence of proteins known as checkpoint proteins. Since melanoma cells are almost normal, they usually have many of these proteins and therefore cannot be attacked. Substances that inhibit these proteins make cancer cells more recognizable to immune cells.
PD-1 is a protein that helps immune cells recognize normal cells. Once the protein is inhibited, immune cells can attack the apparently normal melanoma cells.
CTLA-4 is yet another protein. It works by controlling the activities of immune cells known as T-cells. Once the protein is blocked, T-cells work much actively than they normally would have.
These are proteins used to generally boost the immune system. Boosting means production of more immune cells and such.
As the name suggests, this drug comes in form of a cream. It works by stimulating immune cells in a local area of the body.
Vaccines are mild forms of disease causing organisms. Once administered, they stimulate the immune system to fight against any invading germs or abnormal cells such as melanoma cells.
Oncolytic virus therapy
Viruses are only active once inside host cells. The problem is that they usually destroy the host cells sometimes after invasion. Some viruses are altered in the laboratory and used to destroy cancer cells in the same way.
Melanoma histology is very important especially when dealing with amelanotic melanoma, where tumors lack the normal brown or dark pigmentation.
Melanomas are usually found to be without symmetry, lacking in regular architectural design, with random concentrations of melanocytes and exhibiting signs of normal cell maturation and division.
Nodular melanoma, which is the most invasive form, is seen to have large cells or epithelioid cells. For clinical purposes, Breslow’s thickness is used to describe how thick the tumor is. It is the measure of a tumor from the granular layer to its deepest tip. Clark level can also be used to describe the anatomical invasion level of a tumor in simpler terms. It tells whether a tumor has reached the dermis and the subcutaneous layer. See how fast does melanoma spread for more details.
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