How can I determine if my mole is dangerous?

Moles, or naevi, are clusters of melanocytes, the cells responsible for melanin production. Although most are benign, some can progress into melanoma, a dangerous form of skin cancer. Indeed, in a benign mole, the melanocytes proliferate locally but maintain some control over their growth and differentiation. However, following certain genetic mutations, these cells can escape regulatory mechanisms and proliferate uncontrollably, leading to melanoma.

One of the most common mutations in melanomas involves the BRAF gene, found in approximately 50% of cases according to a study by BOSENBERG and his team. This mutation is accompanied by a strong activation of the MAPK signalling pathway, notably involved in cellular growth. The BRAF gene mutation is not the only one responsible for the formation of a melanoma from a mole, others involving the NRAS or p16 genes can disrupt the cell cycle and lead to this form of skin cancer.

Most moles remain stable over time, but some may evolve in a concerning manner and be precursors to cancerous lesions. This is particularly the case for initially smooth and regular moles that become bumpy, grainy or thicken. A rough texture without an apparent mechanical cause should not be overlooked and should be subject to a medical consultation. Similarly, it is recommended to have moles with irregular edges or whose colour has changed or is unusual examined.

Generally, a mole that changes over a few weeks or months should be monitored.

Furthermore, it's important to note that a mole should not normally cause any pain, itching, redness, or any other signs of inflammation. If this is the case, it may indicate that an underlying inflammatory process is taking place at the mole site. Indeed, abnormal activation of the immune system in this area could be a sign of a concerning progressive process. Similarly, while progressive depigmentation of the mole may be appreciated for aesthetic reasons, it could actually reveal an alteration of the melanocytes. In fact, in some cases, the immune system attacks these cells for no apparent reason, leading to their destruction and a loss of skin colouration, through a mechanism similar to what occurs in the case of vitiligo.

Another sign not to overlook, potentially indicating a dangerous mole, is spontaneous bleeding. This sign is particularly suggestive when accompanied by oozing or a crust that does not heal. It's important to note that we are specifically referring to bleeding without physical trauma. A mole that bleeds when it catches on jewellery or a zip should not be a cause for concern, provided the area is properly disinfected and protected with a dressing.

Finally, it is crucial to pay attention to the emergence of new moles around an existing nevus as this may suggest a beginning of abnormal melanocyte spread into the surrounding tissues. This phenomenon is particularly concerning when the new lesions have irregular characteristics. The ABCDE method, outlined below, remains a practical tool and a reference for assessing the appearance of one's moles.

Having one or more risk factors increases the likelihood of developing melanoma. However, this does not mean that individuals without risk factors are protected and should not monitor their moles.

An important risk factor for the development of atypical moles or melanomas is heredity. If a family member, particularly a first-degree relative, has had a melanoma, the risk of developing this type of skin cancer is increased, due to specific genetic mutations passed down from generation to generation. Similarly, individuals with light skin, eyes, or hair are naturally more vulnerable to melanomas, due to their increased sensitivity to UV rays. General sun exposure and history of sunburns are also a major risk factor for the development of a melanoma. This is why artificial tanning is so dangerous. According to a study published in 2011 in the journal Progress in Biophysics and Molecular Biology, exposure to artificial UV rays before the age of 30 increases the risk of having a melanoma by 75%.

Individuals with numerous moles on their body, more than 50, are also more likely to have a dangerous nevus. Age is also a risk factor, with melanomas most often appearing after the age of 40, although some develop earlier. Finally, certain hereditary diseases, such as Werner syndrome which prematurely ages the skin, or xeroderma pigmentosum which prevents the skin from repairing sun damage, increase the risk of melanoma formation.