What are the causes and risk factors of melanoma ?
The risk factors for skin melanoma are multiple. Some of these factors are directly related to an individual's constitution (constitutional factors), while other factors are related to the environment (environmental factors). It is the interaction between constitutional and environmental factors that will lead to the development of skin melanoma.
Environmental factors
Prolonged exposure to ultraviolet (UV) rays is the main environmental risk factor. This exposure mainly occurs from the sun.
Sudden exposures that lead to sunburns during childhood or adolescence appear to be the most dangerous. In the case of sunburns during childhood, the risk of developing melanoma later in life doubles (source: arcagy.org).
Tanning lamps, especially those used in tanning booths, are another source of UV radiation, and the increased risk of melanoma associated with these lamps has been clearly demonstrated. Regular users of tanning booths therefore have an increased risk of melanoma, which they will develop at a younger age.
UVA or PUVA phototherapy used in the treatment of psoriasis is also a risk factor for melanoma when used at high doses.
Patients with weakened immune systems are at increased risk of developing melanoma. This includes patients on immunosuppressive treatment, particularly for organ transplantation, or those with certain diseases such as human immunodeficiency virus (HIV) infection.
Patients who have had a blood cancer (hematologic malignancy) such as Hodgkin lymphoma or small-cell B lymphoma also have an increased risk of melanoma.
Constitutional factors
Among constitutional factors, a congenital disease (a disease that appeared in utero and is present at birth), xeroderma pigmentosum, is associated with increased sensitivity to X-rays and a higher risk of melanoma. Patients with this rare condition are unable to repair DNA damaged by UV rays.
💡 DID YOU KNOW ?
DNA is a collection of 3 billion molecules found in the nucleus of the 30 trillion cells that make up our body. This DNA is composed of a sequence of 4 different elements named A, T, G, and C, after the first letters of their full names. It forms a double helix and contains all the information necessary for the functioning of each cell. This information is contained in small DNA fragments called " genes ". There are approximately 21,000 genes that determine the function of a cell and the production of proteins, which are essential components of cells.
Mutations can occur in DNA, changing one element to another within one or several genes. These mutations can be passed from a parent to a child ( hereditary genetic mutations ) or occur spontaneously in an individual during their lifetime ( sporadic mutations ). For instance, UV rays can induce sporadic mutations in the DNA of skin cells. Some mutations can increase the risk of developing cancers.
People with congenital melanocytic nevi also have an increased risk of melanoma. A congenital melanocytic nevus is a birthmark or mole present at birth. The risk is higher if the birthmark or mole has a diameter of more than 20 cm in an adolescent or adult.
Similarly, individuals with many nevi, large nevi (greater than 6 mm), or numerous freckles have an increased risk of melanoma.
Among other constitutional factors, individual sensitivity to the sun (phototype) is a risk factor for melanoma. In fact, the lighter the skin, the more significantly it is exposed to melanoma.
Finally, it should be noted that approximately 10% of melanomas occur in the context of familial melanoma, defined as at least two melanomas in first-degree relatives (parent, sibling, child). This familial predisposition may result from a genetic predisposition due to mutations that are passed down from generation to generation: 5 to 25% of families with a higher risk of melanoma have mutations in the CDKN2A gene. This familial predisposition may also result from the family's lifestyle (sun exposure), chance, or an association between genetic predisposition, lifestyle, and chance.
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Article updated on Nov 19, 2024
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