Melanoma: risk factors
Pigmented nevi, nevoids and skin lesions should attract special attention from dermatologists and doctors of other specialties.
Every year the number of cases of cancer increases in the world. The number of malignant skin tumors – melanomas – has tripled recently. Let's talk about the types of malignant neoplasms and risk factors for melanomas.
Types of malignant skin tumors
The main types of malignant skin tumors are melanoma, basal cell and squamous cell carcinoma. The last two diseases are among the most common types of cancer. They make up 90% of all malignant skin tumors. As a rule, these diseases occur in people over 50 years of age on open areas of the body (face, neck, shoulders, forearm, outer side of the palms). And most often the main reason for this is many years of excessive exposure to the sun.
- Basal cell carcinoma is the most common malignant skin tumor (accounting for 70% of all malignant skin tumors). It is characterized by local infiltrating (or invasive) growth with destruction of surrounding tissues, but it rarely metastasizes. Most often, this type of tumor is easily removed surgically or eliminated using cryodestruction.
- Squamous cell carcinoma (spinocellular carcinoma) is a malignant tumor of the skin and mucous membranes. It is observed less frequently (20% of cases). Sometimes it develops on so-called precancerous lesions, actinic keratoses, as well as on scars from burns or chronic ulcers. Squamous cell carcinoma is more aggressive than basal cell carcinoma and can spread to lymph nodes and other organs. As with basal cell carcinoma, spinocellular carcinoma, if detected early, is treated with surgery, usually under local anesthesia. Delayed intervention can lead to complex surgery and even injury.
- The most dangerous malignant neoplasm of the skin is melanoma due to the high probability of metastasis. It can occur in people of any age, but is rarely seen in children. A typical location is the torso in men and legs (lower legs) in women. Most often, melanoma develops from a pigmented formation, but can also occur on clean skin.
The risk of melanoma increases many times over due to frequent sunburn in childhood and periodic intense sun exposure in adulthood (for example, during vacations).
Melanoma is curable if diagnosed early, when the tumor is not very large and its development remains local, without the formation of metastases. Treatment in this case consists of cutting out the tumor under local anesthesia. Late-diagnosed melanoma is usually fatal because it quickly metastasizes and existing treatment methods are no longer effective.
Risk factors
The main risk factor is sun exposure
The sun undoubtedly plays an important role in our lives, it has a beneficial effect on physical and psychological well-being, improves mood and promotes the production of vitamin D in the body. But a few minutes a day is enough to enjoy its benefits.
In addition to the risk of cancer, the sun can cause the development of severe eye pathologies (cataracts, retinal diseases) and premature aging of the skin. Another consequence of excessive ultraviolet radiation is the weakening of the human body's immune system.
There are three types of UV rays - UVA, UVB and UVC, which differ in intensity, wavelength and ability to penetrate the skin to different depths. UVC rays, which have the shortest wavelengths (200-290 nm), pose the main danger because they have the highest energy. Fortunately, they linger in the stratosphere. UVB rays have a wavelength in the range of 290–320 nm and reach the Earth's surface by penetrating the ozone layer. In human skin, UVB rays reach the epidermis but do not penetrate the dermis. They have a powerful destructive effect on cells, causing mutations at the level of its genes, and are responsible for many acute and chronic side effects associated with exposure to sunlight, in particular sunburn, light-induced cell damage, and skin cancer. The wavelength of UVA rays ranges from 320–400 nm. Among the entire UV spectrum, they have the lowest energy, but at the same time the maximum penetrating ability. In human skin, UVA rays reach the middle layers of the dermis. They are most often responsible for premature aging of the skin and probably contribute to the malignant degeneration of cells.
At the same time, our body protects itself by accumulating pigment – melanin – in skin cells. We haven’t understood anything yet, haven’t felt anything, but in the outer layer of the skin the fight for our lives has already begun. The more pigment, the more difficult it is for the rays to penetrate into the subcutaneous layers in order to carry out their destructive effect, causing the breakdown of protein molecules, and therefore the death of the tissues themselves. Within 6-10 hours, redness of the skin appears - erythema, which changes to pigmentation within 3-5 days due to the accumulation of melanin. Thus, moderate tanning increases the protective properties of the skin.
However, this natural protection filters only part of the ultraviolet radiation. Repeated sun exposure damages skin cells and destroys DNA. Fortunately, cells have an adaptation mechanism that allows them to repair the damage they have suffered (enzyme systems, vitamin C, vitamin E, trace elements, in particular selenium). But this natural ability to repair itself is not inexhaustible. With prolonged and often repeated exposure to the sun, the skin cannot fully protect itself from the damage caused by the received dose of UV radiation. And when damaged cells lose their ability to regenerate, mutations can occur, which, in turn, lead to their cancerous degeneration.
Sunbathing in childhood
World statistics show that excessive sun exposure in childhood is a determining risk factor for melanoma in adulthood. Indeed, the skin of babies is more sensitive and delicate - its epidermis is not yet fully formed. However, it is precisely this that provides protection from the first blows of external aggression. With a thin epidermis, the skin retains moisture less well and becomes dry under the influence of the sun and sea water.
In addition, children take longer to develop a system of protection from sunlight. The cells that produce the dark protective pigment melanin begin to function effectively only by the third year of life. Before this period, the influence of the sun leads to redness, irritation of the skin and the local appearance of age spots, that is, the tan forms unevenly. At the same time, all organs and tissues are just developing, and if they are subjected to destruction by ultraviolet radiation, the consequences can be very sad.
It is believed that the majority of lifetime sun exposure occurs before the age of 18 years, as children and adolescents spend more time outdoors than adults. This circumstance confirms the need to prevent the risk associated with excessive sun exposure at a young age.
Hereditary factor
The increased risk of melanoma is also associated with a person’s constitution. Factors that may indicate the existence of such a risk include a family history of skin cancer, skin and hair color, and the number and type of nevi (moles).
A family history of melanoma is an important risk factor. 5–10% of such cases occur in a family context. This is due to genetic characteristics: for example, in 44% of cases of familial melanoma in France, a hereditary mutation of the P16 gene was identified.
It is believed that the risk doubles or triples if a first-degree relative (parents/children, brothers/sisters) has had melanoma. That is why family members who have not been spared by this problem must be constantly monitored at the dispensary.
Skin type and number of moles
However, not all people react to the effects of the sun to the same extent. Thus, those with fair skin are at greater risk of developing melanoma during intense radiation due to their relative lack of pigmentation. However, dark skin is also susceptible to the harmful effects of UV rays, even if it contains more protective pigments.
To determine the length of sun exposure and choose protective measures, it is important to determine your skin type. An existing classification that distinguishes skin phototypes depending on their sensitivity to the effects of UV radiation. This allows the risk to each individual to be assessed and the appropriate protection to be determined. Six phototypes have been identified according to skin color and hair color: the lower the phototype, the more carefully a person needs to protect themselves from the sun.
An indisputable risk factor is also the presence on the body of numerous (50 or more) nevi (moles) larger than 2 mm in size, due to which the likelihood of the disease increases 4–5 times. Atypical (large and irregular) or congenital nevi also contribute to the development of melanoma.
There are a number of risk factors that play a significant role in the pathogenesis of the disease, which can be exo- and endogenous in nature. One of these factors is solar radiation, especially for persons with congenital or acquired nevi, Dubreuil's melanosis or other neoplasms and skin lesions. Other physical factors of pathogenesis include ionizing radiation, chronic irritations, burns (especially sunburn received in childhood and adolescence), frostbite, chemical, temperature or mechanical injuries to nevi, including their self-medication and inadequate cosmetic interventions. Genetic factors of an ethnic order, endogenous constitutional characteristics and the nature of pigmentation (such as the color of skin, hair, eyes), the presence of freckles on the face and hands, the number, size and shape of moles on different parts of the body are of great importance. Thus, melanoma is more common and has a worse prognosis in blondes and redheads. Melanoma is rare in the black population, and in this group of patients the skin of the fingers and toes or the palms and soles is usually affected. The state of endocrine function and hormonal changes are essential in pathogenesis. Puberty, pregnancy, and menopausal changes in the body are critical periods that are regarded as risk phases for the activation and malignancy of pigmented nevi.
In the vast majority of cases (approximately 70% of patients), melanoma develops at the site of congenital or acquired nevi, Dubreuil's obligate pre-melanoma skin disease, and only in 28-30% - on unchanged skin (melanoma cutis de nomo). Pigmented nevi and pigmented skin formations occur in 90% of the population, and their number ranges from a few to several dozen. A practicing oncologist, dermatologist, as well as doctors of other specialties, therefore, very often have to encounter a variety of pigmented skin lesions, and among them melanoma accounts for 0.5-3%.
Dangerous ABC
Benign non-cellular nevi include acquired non-cellular nevi (birthmarks), formed by an accumulation of nevus cells in the epidermis and dermis. The most common skin neoplasms are found in representatives of the white race; on average, about 20 nevi are found in an adult. They appear in early childhood and reach their maximum number in adolescence. Acquired noncellular nevi are divided according to the localization of accumulations of nevus cells in the epidermis and dermis: borderline; complex (mixed); intradermal.
Noncellular nevi, like melanoma, can have a similar shape, size, borders, color and uniformity of color. Therefore, any small pigmented formation must be given attention during examination and dermatoscopy. Indications for removal of nevi are localization in which the risk of malignant degeneration is increased (scalp, soles, perineum, mucous membranes), as well as the appearance of clinical signs of dysplasia. For ease of remembering, these characteristics have been grouped in alphabetical order - ABCDE.
A - Asymmetry (asymmetry). Normal moles are completely symmetrical. If you draw an imaginary line through their middle, then the halves should be the same; in suspicious cases, they differ from each other.
B - Border. Normal moles have a clear border; suspicious moles have blurred and/or uneven edges.
C - Color (color). Moles that are more than one color or have several different shades are suspicious and should be seen by a doctor. Normal birthmarks are usually one color, although they can include lighter and darker shades.
D - Diameter. If the mole is larger than a pencil eraser (about 6 mm), it should be examined by a doctor. This is also true for those spots that do not have any other deviations (color, borders, asymmetry).
E - Evolution (changes). If birthmarks have changed their number, symmetry, borders or color, they must be shown to a doctor.
It is worth remembering that a malignant mole does not necessarily differ from a normal mole according to each of these criteria. One difference is enough to regard a mole as suspicious, in which case it should be shown to a dermatologist.
Benign nevi
Nevus Spitz (juvenile melanoma, juvenile nevus, epithelial and spindle cell nevus) is a rare benign fast-growing pigmented formation, more common in children. The formation is a small, less than 1 centimeter in diameter, dome-shaped hairless nodule of pink-red or yellow-brown color, most often localized on the face. The risk of malignant degeneration occurs with puberty. It is often impossible to distinguish nevus Spitz from melanoma clinically; to establish a diagnosis, the clinician and pathologist must have extensive clinical experience. It is advisable to surgically excise the tumor from the edge of the nevus to the resection boundaries of at least 5 mm, with mandatory histological examination.
Halonevus (nevus of Setton or Sutton) is a noncellular nevus surrounded by a depigmented rim. Some authors classify halonevus as one of the types of vitiligo. Depigmentation is caused by a decrease in the melanin content in melanocytes and the disappearance of melanocytes themselves from the epidermis. The clinical picture of halonevus is typical: a hyperpigmented node surrounded by a depigmented rim of skin. No treatment required. Observation by a specialist is recommended, since in rare cases melanoma can also be surrounded by a hypopigmented rim.
Blue nevus (blue nevus, blue nevus of Jadassohn-Tiche) appears in adolescence or a little later. It is a round nodule of dense consistency protruding above the skin level, no more than 1 cm in diameter, from blue to bluish-black. Most often, blue nevus occurs on the face, foot, sole, buttocks, and lower legs. Usually the formation is single, but cases of numerous blue nevi have been described. Treatment is not carried out if the nevus is up to 1 cm in size and there are no clinical signs of transformation into melanoma. If a nevus suddenly appears or changes in its appearance, it is advisable to excise the tumor and conduct a histological examination.
Nevus of Ota (dark blue orbital-maxillary nevus). Typical localization is the face (area of innervation of the I and II branches of the trigeminal nerve). It occurs in most cases among representatives of the Mongoloid race. It consists of one large or many merging spots of black-bluish color, located in the area of the cheek, upper jaw, and zygomatic arch. In this case, pigmentation is required in various parts of the eye: conjunctiva, sclera, iris. Sometimes the process involves the red border of the lips and the mucous membranes of the nose, soft palate, pharynx, and larynx. Often found together with Nevus of Ito, which has similar manifestations. With nevus of Ota and nevus of Ito, patients should be under constant medical supervision and examined every 3 months. Surgical intervention is usually not indicated.
Scattered nevus (naevus spilus) is a hyperpigmented spot from 1 to 15 centimeters in diameter, on the surface of which there are small dark brown spots or papules. It develops throughout life and transforms into melanoma extremely rarely. There is no treatment.
A café au lait nevus is a hyperpigmented spot. These types of nevi can be congenital or appear in the first three years of life. In some cases, they are clinical manifestations of neurofibromatosis. If the existence of a spot is a constitutional feature, then, as a rule, it does not change throughout life. In neurofibromatosis, the number and size of spots increase with age. At the site of a café au lait nevus, melanoma does not develop.
Becker's nevus (pigmented pilaris epidermal nevus) is a hyperpigmented patch with increased hair growth. They develop during puberty against the background of an increase in androgen levels, so they occur more often in men. It is a large plaque with an uneven, slightly warty surface and uneven, jagged borders. A linear arrangement of the nevus and increased growth of pigmented long hair in the area of the lesion are often observed. Becker's nevus does not degenerate into melanoma, but its clinical signs are similar to giant congenital noncellular nevus, which has a high risk of transformation into melanoma.
Melanoma precursors
In 30% of cases, melanomas develop from a previous pigmented formation. Their existence in patients is a risk factor for the development of melanoma. Precursors to melanoma include:
- congenital noncellular nevus;
- dysplastic nevus;
- lentigo maligna (limited melanosis of Dubreuil).
Congenital noncellular nevus is a benign pigmented formation that consists of nevus cells and can transform into melanoma. It is usually discovered at birth. Depending on their size, congenital noncellular nevi are divided into small (diameter up to 1.5 cm), large (more than 1.5 cm) and giant (occupying any anatomical area or most of it).
Small and large congenital noncellular nevi are usually a plaque raised above the skin, sometimes covered with coarse terminal hair. The shape of the nevus can be smooth or wrinkled, lumpy, folded lobular. The color is light or dark brown. Localization - any. The risk of developing melanoma during life with a small nevus is 1-5%, with a large one - 6.5%. It is advisable to remove small and large congenital noncellular nevi before the patient reaches 12 years of age. It is advisable to carry out treatment only after consultation with an oncologist.
Giant congenital pilaris pigmented nevus usually affects the extremities and trunk, and is rarely found on the face. The nevus increases in size relatively quickly as the child grows, reaching a size from 10 to 40 cm or more. Its surface is uneven, warty, with cracks. Hypertrichosis is often observed. The color of the formation is from gray to black. A giant nevus may be accompanied by other congenital malformations, for example, hydrocephalus, neurological disorders and the occurrence of primary melanoma of the pia mater, which is very important in diagnostic terms. The transformation of this nevus into melanoma occurs in 1.8-13% of patients. Malignancy of giant pigmented nevi in children is especially dangerous - in such cases they should cause caution.
Dysplastic nevus (atypical nevus, atypical birthmark, Clark's nevus) is an acquired pigment formation characterized by an increased risk of malignancy due to the persistence of proliferative activity of immature melanocytes in the epidermis and cell atypia of varying severity, found in 5% of the white population. Individuals with dysplastic nevi are considered to be at very high risk of developing melanoma. This nevus occurs in almost all patients with familial melanoma and in 30-40% of patients with sporadic melanoma. It is located on the skin of the torso, arms and legs, and very rarely on the face. It is a spot with a separate, slightly raised area in the center above the skin level.
In the presence of a central papular component, these nevi are compared in appearance to a “fried egg”; the size of the lesion is more than 6 mm. They differ from ordinary acquired nevi in the following clinical signs: irregular shape; larger than ordinary nevi in size; blurred edges, unclear outlines without clear boundaries; usually a flat surface; wide variations in color (the color is uneven, variegated and is characterized by the presence of various shades of brown, reddish and light red). The diagnosis is made on the basis of clinical data and, necessarily, the results of histological examination. Treatment is surgical. Persons who have previously had melanoma, as well as their relatives, should be monitored by a specialist and undergo examination at least every 3-6 months.
Lentigo maligna (Dubray's melanosis, limited precancerous melanosis) is a precursor of melanoma, characterized by the proliferation of atypical melanocytes in the epidermis, and the melanoma developing in its place can sometimes have a more malignant course than non-genic melanoma. Lentigo occurs mainly in old age and develops more often in women. In most cases, the skin of the cheeks, nasolabial folds, nose, forehead, and less commonly the neck, scalp, and back of the hands are affected. The disease usually begins with a small pigment spot that slowly spreads along the periphery. A mature lesion is characterized by the presence of a single formation, with uneven outlines and surface, measuring 2-3 centimeters (in its largest part). Then the focus, developing, acquires blurred boundaries. In its developed state, Dubreuil's melanosis ranges from 2-3 to 5-6 centimeters in diameter, has uneven edges, a flat surface, with papules, nodules, and plaques. The color of the formation is uneven - brown, gray, bluish. Its appearance often resembles a drawing of a geographical map. Characterized by increased pigmentation along the periphery of the lesion. The transition to melanoma is indicated by the appearance of a variegated color of the pigmented lesion, while the borders become uneven and the shape becomes irregular. Patients in this group of patients should be sent for consultation to an oncological surgeon.
Malignant pigmented tumors
Melanoma (synonyms: melanoblastoma, melanocytoma, neocarcinoma) is one of the most malignant tumors. Melanoma is considered a special form of malignant tumor due to its very pronounced differences from other skin tumors. It develops from melanocytes - pigment cells located mainly in the basal layer of the epidermis and producing a specific polypeptide melanin.
According to various data, the incidence of skin melanoma ranges from 1 to 30 or more per 100,000 population per year, and the frequency is 1-4% among all malignant skin tumors. In recent years, there has been a significant increase in the incidence of skin melanoma in various regions of the world: the annual incidence rate increases in different countries by 2.6-11.7%. Most researchers are convinced that the incidence of melanoma doubles every ten-year period. According to expert forecasts, in the 21st century, a significant increase in morbidity is expected throughout the world, and mortality from melanoma is approximately 0.74% of all deaths from malignant tumors. However, according to some reports, in some countries the incidence and mortality from melanoma is increasing faster than from malignant neoplasms of other sites, with the exception of lung cancer and breast cancer in women. Moreover, the diagnosis of melanoma, especially its early forms, cannot be considered satisfactory.
According to world statistics, the vast majority of patients with skin melanoma are 30-60 years old. In most of Europe, women are more often affected, and in Australia and the United States, incidence rates for women and men are equal. The predominant localization of melanomas in women is the lower extremities (lower leg), in men - the torso (usually the back); In both sexes of the older age group (65 years and older), melanoma is localized mainly on the skin of the face. However, it can occur on any part of the skin (terminal phalanges of the fingers, vulva, rectum, etc.), and in approximately 2% of cases (according to some data - up to 20%), the primary focus cannot be identified, and the clinical picture is caused by metastases.
Literature:
- Tatyana Svyatenko, Doctor of Medical Sciences, Professor of the Department of Skin and Sexually Transmitted Diseases, Dnepropetrovsk Medical Academy
- Natalya Mikhailets, dermatovenerologist, 17th city hospital (Dnepropetrovsk)
- Cosmetologist No. 6, 2011
- LNE 3 (67)