Cutaneous malignant melanoma

It originates in melanocytes, the cells that produce melanin, the pigment that gives color to the skin and protects it from UV rays. 90% of cases appear on the skin, although it can also manifest in the eyes or, rarely, inside the body. It accounts for only 1% of skin cancers, and while it is associated with a worse prognosis, if detected early, it has a high chance of being cured.

Skin cells develop in a controlled and orderly manner. New cells push the old ones toward the surface of the skin where they die and are shed from the body. When some cells acquire DNA damage, it can trigger uncontrolled growth of new cells, leading to skin cancer.

Most of the time, genetic changes related to melanoma are acquired during life and are not passed down (not inherited). In some cases, they occur randomly in a cell without a clear cause, while in others, they likely result from an external cause. Therefore, it is likely that a combination of environmental and genetic factors leads to the development of melanoma.

Ultraviolet (UV) rays, especially type B but also type A, are the main cause of melanoma as they can damage the DNA of skin cells. However, UV light does not cause all melanomas, especially those that occur in parts of the body not exposed to sunlight, so other factors may influence melanoma risk.

The following factors may increase a person's risk of developing melanoma:

• Sun exposure: Living at high altitudes or in areas with intense sunlight year-round increases the risk, as does spending extended periods outdoors at midday.
• Indoor tanning in tanning beds, tanning salons, or sun lamps. Their use is strongly discouraged.
• Moles: People with many moles or unusual, large, irregularly shaped and colored moles (dysplastic or atypical nevi) are at higher risk.
• Fair skin: People with fair skin, blonde or red hair, blue eyes, and freckles are at higher risk of developing melanoma. This risk is also higher in people who tend to burn rather than tan.
• Previous skin cancer: People who have already had melanoma or basal or squamous cell skin cancer are at greater risk of developing melanoma.
• Ethnicity: While it can develop in individuals of any ethnicity, people of Caucasian descent have a 20-fold higher risk than those of African descent.
• Age: It occurs more frequently in young adults than many other types of cancer. The median age of diagnosis is around 50 years old.
• Weakened immune system: Both due to diseases and immunosuppressive treatments, a weakened immune system increases the risk of developing skin cancer, including melanoma.

Additionally, and less frequently, genetic changes can be inherited from parents that increase the risk of melanoma. About 10% of people with melanoma have a family history of the disease, and the risk of developing melanoma is 2 to 3 times higher than average if a close relative is affected. This risk increases if several family members living in different locations have been diagnosed with melanoma. Additionally, hereditary familial forms of melanoma due to changes in specific genes such as CDKN2A, CDK4, P53, and MITF, though rare, have been described. Other hereditary conditions (Xeroderma Pigmentosum, Li-Fraumeni Syndrome, or hereditary breast and ovarian cancer, among others) are also associated with a higher risk of melanoma.

Melanomas can form anywhere on the body, although they most commonly appear in areas that have been exposed to the sun (back, legs, arms, or face). They can also occur in areas without sun exposure, such as the soles of the feet, palms of the hands, or nail beds, although this typically occurs in individuals with darker skin.

Changes in the size, shape, color, or texture of a mole are often the first warning signs. These changes may occur in an existing mole, or as a new or unusual-looking mole; however, it can also appear on normal-looking skin. In 75-80% of cases, melanoma appears without a pre-existing mole.

The ABCDE rule summarizes the suspicious characteristics of a pigmented skin lesion:

• Asymmetry: The lesion is NOT round.
• Borders: The edges are irregular.
• Color: The lesion has different, non-uniform colors.
• Diameter: The lesion is larger than 6mm in size.
• Evolution: The characteristics have changed over time.

Although the causes of melanoma are still being clarified and its prevention remains uncertain, there is no consistent way to completely avoid its development. However, it is possible to act on known factors to reduce the risk as much as possible. The most important way to reduce the risk of melanoma is to protect yourself from UV exposure:

• Limit or avoid direct sun exposure during midday hours when the sun's radiation is strongest, depending on geographic location. Preferably stay in the shade.
• Wear sun-protective clothing, hats that cover the face, neck, and ears, as well as UV-protective clothing and sunglasses with UV protection.
• Apply plenty of broad-spectrum sunscreen against UVA and UVB radiation with a sun protection factor (SPF) of at least 30 on the entire body, even on cloudy days, every 2 hours or more frequently when sweating or swimming.
• Avoid sun lamps, tanning beds, and tanning salons.
• Regularly examine the skin, including self-examinations to check for new lumps or changes in moles, freckles, bumps, and existing birthmarks, and seek professional evaluation.

In these circumstances, it may be necessary to include good sources of vitamin D in your diet or even use supplements.