Melanocytic nevus

Cause

The cause of this condition is not clearly understood, but it is thought to result from a defect in embryologic development during the first 12 weeks of pregnancy. The defect is thought to cause a proliferation of melanocytes, the cells responsible for normal skin color. When melanocytes are produced at an extremely rapid rate, they form in clusters instead of spreading out evenly, resulting in abnormal skin pigmentation in some areas of the body.

Genetics

Genes can influence a person's moles. Dysplastic nevus syndrome is a largely hereditary condition that causes a person to have a large quantity of moles (often 100 or more), with some larger than normal or atypical. This often leads to a higher risk of melanoma, a serious type of skin cancer. Dysplastic nevi are more likely than ordinary moles to become cancerous. While dysplastic nevi are common, and many people have a few of these abnormal moles, having more than 50 ordinary moles also increases the risk of developing melanoma.

In the general population, a slight majority of melanomas do not form in existing moles but rather create new growths on the skin. Somewhat surprisingly, this pattern also applies to those with dysplastic nevi. These individuals are at a higher risk of melanoma occurring not only where there is an existing mole but also in areas without moles. Consequently, such persons need regular examinations to check for changes in their moles and to identify any new ones.

Sunlight

Ultraviolet (UV) light from the sun causes premature ageing of the skin and skin damage that can lead to melanoma. Researchers hypothesized that overexposure to UV, including excessive sunlight, may play a role in the formation of acquired moles. However, more research is needed to determine the complex interaction between genetic makeup and overall UV exposure. Some strong indications supporting this hypothesis (but falling short of proof) include:

• The relative lack of moles on the buttocks of people with dysplastic nevi
• The known influence of sunlight on freckles (spots of melanin on the skin, distinct from moles)

Studies have found that sunburns and excessive sun exposure can increase risk factors for melanoma. This is in addition to the higher risk already faced by individuals with dysplastic nevi (the uncertainty is regarding acquiring benign moles). To prevent and reduce the risk of melanoma caused by UV radiation, the American Academy of Dermatology and the National Cancer Institute recommend:

• Staying out of the sun between 10 a.m. and 4 p.m. standard time (or whenever one's shadow is shorter than one's height)
• Wearing long sleeves and trousers
• Wearing hats with a wide brim
• Applying sunscreens
• Wearing sunglasses that have UV-deflecting lenses

Diagnosis

Clinical diagnosis can be made with the naked eye using the ABCD guideline or by using dermatoscopy. An online-screening test is also available to help screen out benign moles.

Classification

Melanocytic nevi can mainly be classified by depth, being congenital versus acquired, and/or specific dermatoscopic or histopathologic patterns:

Depth

Congenital versus acquired

• Congenital nevus: Small to large nevus present at or near time of birth. Small ones have low potential for forming melanomas, however the risk increases with size, as in the giant pigmented nevus.
• Acquired nevus: Any melanocytic nevus that is not a congenital nevus or not present at birth or near birth.

Specific dermatoscopic or histopathologic patterns

Recurrence

Recurrent nevus: Any incompletely removed nevus with residual melanocytes left in the surgical wound. It creates a dilemma for the patient and physician, as these scars cannot be distinguished from a melanoma.

Differentiation from melanoma

It often requires a dermatologist to fully evaluate moles. For instance, a small blue or bluish-black spot, often called a blue nevus, is usually benign but often mistaken for melanoma. Conversely, a junctional nevus, which develops at the junction of the dermis and epidermis, is potentially cancerous.

A basic approach to evaluating suspicious moles is found in the mnemonic A-B-C-D, used by institutions such as the American Academy of Dermatology and the National Cancer Institute (NCI). The letters stand for Asymmetry, Border, Color, and Diameter. Sometimes, the letter E (for Elevation or Evolving) is added. According to the American Academy of Dermatology, if a mole starts changing in size, color, shape or, especially, if the border of a mole develops ragged edges or becomes larger than a pencil eraser, it would be an appropriate time to consult with a physician. Other warning signs include a mole, even if smaller than a pencil eraser, that is different from the others and begins to crust over, bleed, itch, or become inflamed. Such changes may indicate the development of melanomas.

Another method of melanoma detection is the "ugly duckling sign". It is simple, easy to teach, and highly effective in detecting melanoma. Simply, correlation of common characteristics of a person's skin lesion is made. Lesions which greatly deviate from the common characteristics are labeled as an "ugly duckling", and further professional exam is required. The "little red riding hood sign", suggests that individuals with fair skin and light colored hair might have difficult-to-diagnose melanomas.

Extra care and caution should be rendered when examining such individuals, as they might have multiple melanomas and severely dysplastic nevi. A dermatoscope must be used to detect "ugly ducklings", as many melanomas in these individuals resemble non-melanomas or are considered to be "wolves in sheep's clothing". These fair-skinned individuals often have lightly pigmented or amelanotic melanomas, which will not present easy-to-observe color changes and variation in colors. The borders of these amelanotic melanomas are often indistinct, making visual identification without a dermatoscope very difficult.

People with a personal or family history of skin cancer or of dysplastic nevus syndrome (multiple atypical moles) should see a dermatologist at least once a year to be sure they are not developing melanoma.

Management

First, a diagnosis must be made. If the lesion is suspected to be skin cancer, a skin biopsy may be done before considering removal. Alternatively, an excisional biopsy with complete removal of the lesion may be done. Other reasons for removal may be cosmetic or because a raised mole interferes with daily life (e.g., shaving).

If a melanocytic nevus is suspected of being a melanoma, it needs to be sampled or removed via skin biopsy, and sent for microscopic evaluation by a pathologist. Depending on the size and location of the original nevus, a complete excisional skin biopsy or a punch skin biopsy can be done. Removal can also occur by shaving. Shaving leaves a red mark on the site but changes to the patient's usual skin color in about 2 weeks. However, there might still be a risk of spread of the melanoma, so the methods of melanoma diagnosis, including excisional biopsy, are still recommended even in these instances. Moles can also be removed by laser, surgery, or electrocautery.

Medical lasers can be used to remove flat moles (those level with the surface of the skin), as well as some raised moles, leaving a scab. Some dermatologists think lasers are not the best method for removing moles because the laser only cauterizes or, in certain cases, removes very superficial levels of skin. Moles tend to go deeper into the skin than non-invasive lasers can penetrate. A second concern about laser treatment is that if the lesion is a melanoma and was misdiagnosed as a benign mole, the procedure might delay diagnosis. If the mole is incompletely removed by the laser, and the pigmented lesion regrows, it might form a recurrent nevus.

For surgery, many dermatologic and plastic surgeons first use a freezing solution, usually liquid nitrogen, on a raised mole and then shave it away with a scalpel. If the surgeon opts for the shaving method, they usually also cauterize the stump. However, freezing should not be done to a nevus suspected to be a melanoma, as the ice crystals can cause pathological changes called "freezing artifacts" which might interfere with the diagnosis of the melanoma.

Electrocautery is a procedure that uses an electrical current to burn moles, skin tags, and warts off the skin. Electric currents are set to a level such that they only reach the outermost layers of the skin, thus reducing the problem of scarring. Approximately 1–3 treatments may be needed to completely remove a mole. Typically, a local anesthetic is applied to the treated skin area before beginning the mole removal procedure.

Mole removal risks

The risks associated with mole removal vary depending on the method employed (e.g., surgical excision, shave removal, or laser therapy). In general, patients may experience mild postoperative discomfort, which is typically manageable with over-the-counter analgesics. Localized redness and the formation of a scab are also common but usually resolve within 1–2 weeks as the wound heals. Third, similar to other surgeries, there is also risk of infection, bleeding, allergic reactions to anesthesia, or even nerve damage. Lastly, the mole removal may leave an uncomfortable scar depending on the mole's size.

Society and culture

Throughout much of human history, individuals with facial moles were often subject to ridicule, superstition, and stigma. Far from being viewed as marks of beauty, facial moles were commonly associated with negative imagery and folklore. In particular, moles located on the nose, cheeks, or chin were frequently linked to witches or other undesirable creatures, reflecting cultural beliefs that cast them as disfiguring or ominous growths rather than natural features.

During the Salem witch trials, warts and other dermatological lesions such as moles, scars, and other blemishes found on accused women were considered evidence of a pact with the devil.

Face mole reading

In traditional Chinese culture, facial moles are used in divination or fortune telling (moleomancy). Moles that can be easily seen may be considered warnings or reminders, while hidden moles may symbolize good luck and fortune. Furthermore, traditional Chinese culture holds that each facial mole indicates the presence of a corresponding mole on another part of the body. For instance, if a mole is present around the mouth, a corresponding mole should be found in the pubic region.