Epidermal nevus

A familiar brown mole, convex or flat depending on its location, the pigment cells of which are located exclusively in the dermis layer (which is visible not visually, but during microscopic examination), is called an intradermal nevus.

In the vast majority of cases, the neoplasm is benign and acquired, and is one of the most common birthmarks. They appear spontaneously, mainly in people over 10 years old, and are located diffusely on the body. By about 30 years of age, the intensive birth of new birthmarks ends, but they can appear and disappear throughout life.

A typical intradermal nevus rises above the skin surface and looks like a dome with clearly defined borders, soft to the touch, or like a papilloma. The higher the convexity, the more dermal component there is in the structure of the mole. Depending on the number of melanocytes, it has a color from light to dark brown. Hairs may grow on the mole.

The presence of moles does not cause any discomfort to their owner. He simply does not notice them. If they begin to change color, size, shape, itch, crack, bleed, then this should be a reason for an urgent visit to the doctor.

Epidermal nevus is a benign developmental defect, which, as a rule, has a dysembryogenetic origin. Three forms of nevus are known: localized, inflammatory, systemic. All of them appear at birth or in early childhood.

Epidemiology

Statistics show that congenital melanocytic nevi are extremely rare - about 1% of newborns or infants of the Caucasian race. The probability of malignancy of small congenital melanocytic nevi is from 1 to 5%. Against the background of giant pigment spots, melanoma develops more often - about every 16th, and in half of the cases at the age of three to five years.

Acquired melanocytic nevi appear after the age of ten. By the time adolescence is reached, almost everyone already has moles, and by the age of 20-25, each representative of the "white" race has approximately 20 to 50 such formations. Asians and Africans have much fewer of them. [ 1 ]

Melanocytic nevi are of interest to clinicians primarily as premelanoma skin lesions. Not every one of them is a source of a tumor. There are still serious differences of opinion on this issue: according to some data, melanoma in most cases is formed from already existing nevi, other studies claim that the vast majority of this aggressive form of cancer occurs in areas of intact skin and even trauma to a benign nevus does not lead to its malignancy. However, researchers note that some types of lesions have a high probability of degeneration. According to the largest Russian medical and diagnostic center, the N.N. Petrov National Medical Research Center of Oncology, of the typical nevi, the highest probability of malignancy is in the complex nevi, it is estimated at 45%. The risk of degeneration at the stage of a borderline nevus is somewhat lower - 34%. A mature epidermal nevus is in last place among them - 16%. Moreover, the majority of nevi (70%) that underwent malignant changes were congenital. [ 2 ]

Causes epidermal nevus

Nevi are tumors and are considered a skin pathology. However, with a large number of moles, you can live in good health to a very old age and die from a disease that has nothing to do with the abundance of pigment spots.

The causes of moles are still being debated. There is no exact answer to the question of why melanocytes transform into nevus cells. But the main risk factors for the occurrence of such transformations have been established: genetic predisposition, changes in hormonal status and excessive insolation. The congenital tumor process is obviously associated with disorders in the differentiation of melanoblasts in the period from the tenth to about the 25th week of intrauterine development of the fetus.

Melanocytes are cells that synthesize the coloring pigment melanin, everyone has them, and almost all representatives of the white race also have moles. But their number varies: some have single moles, while others are simply covered in them. The pathogenesis of the tumor process of the melanogenic system is triggered by certain factors: heredity, sunburn, frequent visits to a solarium, other types of radiation, constant injuries - insect bites, friction, cuts, rashes - of allergic or infectious origin, hormonal surges. It is possible that under the influence of several of them, melanocytes are transformed into nevus cells. These cells are considered the initial stage of tumor progression, which can end in the development of melanoma. However, in general, clusters of such cells - melanocytic nevi or moles, are benign neoplasms and do not become malignant. [ 3 ]

Nevus cells tend to stick together in epidermal nests, where they lose their dendritic processes and undergo a sequential process of "maturation." They are divided into three types according to their degree of maturity:

• epithelioid nevus cells or type A, the “youngest” ones, located in the nests of the border epidermis (lower) and/or dermis (upper), microscopically resemble the cells of the basal layer of the epithelium, but their nuclei are larger and surrounded by abundant eosinophilic cytoplasm;
• lymphocytoid (type B) - more mature and deeper located, round, small (their nucleus and cytoplasm volume are reduced), resembling lymphocytes;
• spindle-shaped or type C - the last stage of maturation, localized in the depth of the melanocytic nevus.

Spindle-shaped nevus cells have the lowest risk of degeneration. [ 4 ], [ 5 ]

Pathogenesis

The mechanism of development of epidermal (intradermal) nevus is step-by-step and corresponds to the successive cytological transformation (maturation, aging) of nevus cells. At first, a border nevus is formed - a formation of altered melanocytes appears in the intraepidermal nests of the lower layer of the epidermis at the border with the dermis. In the process of differentiation, nevus cells "flow in drops into the upper layers of the dermis". When they are found partially in the intradermal, as well as in the upper and deeper layers of the dermis, such a nevus is called complex (mixed or epidermo-dermal). This is the next, second, stage of its development.

The border component may disappear over time, then the nevus cells remain only in the dermal layer – epidermal nevus (the last, third stage of maturation).

Melanocytic nevi can stop at any stage of development and never pass into the next form. Also, the activity of old epidermal formations can resume. The formation of an intradermal melanocytic nevus is associated with the stages of atrophic transformations of melanocytes: melanocyte → nevus cell → fibrous tissue.

In childhood and adolescence, acquired epidermal nevi are more common, localized in nests of the upper layers of the dermis. They practically do not contain fibrosis, they mainly consist of premelanin and restored melanin.

In adults, epidermal nevi are located in deeper layers of the dermis. The cells may lack melanin synthesis, then pronounced fibrosis is detected. Sometimes there is focal activity with melanogenesis in the dermis or borderline with its reverse transformation into complex. In the development of the formation, there is a possibility of spontaneous regression and cessation of activity, as well as malignancy. Therefore, old epidermal nevi with the resumption of borderline activity require oncological alertness and careful examination.

Pathomorphology

Typical elements are warty hyperkeratosis, acanthosis, papillomatosis. In the inflammatory form, nonspecific mononuclear infiltrate is observed in the papillary layer of the dermis, and focal parakeratosis in the epidermis. In localized and systemic forms of nevus, pilosebaceous structures are often encountered, which undergo hypertrophy during puberty. When localized on the scalp, defects can be of a complex structure and contain clusters of hypertrophied apocrine glands. In some cases, systemic nevus is accompanied by acantholytic hyperkeratosis, similar to the bullous variant of congenital ichthyosiform erythroderma. In this case, "granular dystrophy" of epithelial cells with rupture of cellular contacts, perinuclear edema, and an increase in the number of irregularly shaped keratohyaline granules are observed in the spinous layer. In the foci of inflammatory nevus, morphological changes may resemble those in psoriasis.

Symptoms epidermal nevus

A localized nevus is clinically a limited lesion consisting of exophytic single or multiple papillomatous formations, closely adjacent to each other, round, oval or irregular in shape, the color of normal skin or with varying degrees of pigmentation, with a smooth or (more often) warty surface.

Inflammatory nevus usually has the appearance of compacted, linearly grouped elements with a warty surface on an inflamed base, often psoriasiform, sometimes accompanied by itching.

In systemic nevus, the lesions are located linearly, in the form of garlands, mostly monolaterally, sometimes in combination with developmental defects of the eyeballs, skeletal anomalies (especially the bones of the skull) and encephalopathies.

The first signs of a birthmark are visual. It does not hurt, does not itch, and does not cause any other noticeable discomfort.

Externally, an epidermal nevus is a convex, round, oval, molluscum-like growth on the skin, resting on a wide base, or papillomatous - on a leg. The diameter of the formation, in the vast majority of cases, is no more than 10 mm. Its surface can be smooth or warty, covered with hard short hairs, colored in any shades of brown. Some people have flesh-pink or whitish nevi (depigmented).

It is impossible to determine exactly that nevus cells are located in the dermis only by their appearance. Intradermal localization is typical for a mature nevus. It is usually convex (papilloma-like), but a complex nevus also looks the same. The higher the convexity, the more dermal component and the lighter its color. Flat epidermal nevi can be on the palmar or plantar surface due to the thick stratum corneum of the skin in these areas.

Intradermal nevi are benign neoplasms that have passed all three stages of development. At the beginning, melanocytes transform into nevus cells in the zone of border activity - the lower layer of the epidermis on the border with the dermis. Then a small, on average 2-4 mm, flat round pigment spot or nodule (birthmark) appears on the skin, uniform, of varying degrees of saturation of brown color - a border (junctional) nevus. Its borders are clear, even, sometimes wavy, the surface is smooth, the skin pattern (papillary lines) is clearly visible. Border nevus most often appears on the face, back, chest, neck, arms and legs, less often - on the skin of the palms, feet, genitals. It does not manifest itself with any symptoms, except for visual ones. The growth of the formation and the change in color (it becomes more saturated), deep development occurs slowly, imperceptibly. Some border nevi remain within the epidermis – they stop at the first stage of development. Microscopically, a clearly defined cluster of melanocyte nests containing an insignificant amount of pigment is detected in the lower layers of the epidermis. At the border from the dermis side, an increase in the number of cells phagocytizing melanin (melanophages) is determined, as well as a minimal, not too dense infiltrate in the subepidermal zone.

When nevus cells spread into the dermal layer, the second stage of melanocytic nevus development occurs – complex or mixed nevus. External clinical signs of this stage are a more saturated color, a convex shape – the higher the dome, the deeper the nevus cells have spread into the dermis. The surface of a convex mole can be uneven, slightly warty, with bristly hairs growing on it. When examined microscopically, nevus cell clusters are determined in the lower layers of the epidermis and in the dermis.

There are three possible variants of evolution of a complex nevus: into epidermal, into melanoma, and spontaneous regression (only for acquired ones).

The most common among melanocytic nevi are epidermal ones - benign neoplasms of the melanogenic system, located exclusively in the dermis layer. There is no clear classification of them, it is quite contradictory and confusing, but its purpose is also to divide nevi by the degree of melanoma danger. They are divided into types by morphological features - cellular structure and location in the layers of the skin (epithelioid or spindle cell, borderline, complex, intradermal), by appearance (papillomatous, blue, halo nevus, giant), by other features and their combination (cellular blue nevus, dysplastic or atypical, deeply penetrating and others, rare). They are also divided into congenital and acquired. [ 6 ]

Forms

Congenital epidermal nevus is a rarity. As practice shows, congenital nevocellular formations most often belong to complex ones, that is, they are located in two layers of the skin, epidermal and dermal. Congenital nevi are considered melanoma-dangerous, since the vast majority of melanomas developed against the background of congenital nevi, and not acquired ones.

Congenital nevocellular formations include those that are detected immediately after birth or somewhat later, but in infancy. The size of the nevus can vary: from small (up to 15 mm) to giant - more than 20 cm. Usually their surface is slightly convex, soft to the touch. Further, there is a great variety: localization - any part of the body; borders - clear, wavy, jagged or blurred; surface - smooth with a skin pattern, with tubercles, warty, with papillae or lobules; color - different shades of brown, when spreading into the reticular layer of the dermis - bluish-gray without a skin pattern (blue nevus); round or oval, sometimes undefinable in shape. Congenital nevi can be single and multiple - then one of them is larger than the others. Hairs can also grow on the surface of the nevus, which appear somewhat later.

Small congenital epidermal nevi in adults are visually no different from acquired ones. A larger size may indicate a congenital nature, for example, moles with a diameter of more than 15 mm are currently considered congenital or atypical. Special studies reveal some morphological features of the location of nevus cells in the layers of the dermis, confirming the congenital nature of the formation: their detection in the lower layers of the reticular layer, subcutaneous tissue, and skin appendages.

Giant congenital nevi usually have an epidermal-dermal location.

Intradermal melanocytic nevus is also called pigmented, since it consists of altered melanocytes - cells that synthesize coloring pigment. The formation differs in color from the rest of the skin surface. Depending on the content of melanin in the cells, epidermal pigmented nevus can have a color from light reddish to dark, almost black. The cells that make up the neoplasm, altered melanocytes, are called nevus cells, respectively, the birthmark itself, located in the dermis, is called epidermal nevus. All these names are synonyms and do not denote different types of moles, but one and the same, characterizing it from different sides.

Intradermal papillomatous nevus is one of the subtypes of pigmented formation, distinguished by its appearance. It is convex, consists of elongated processes, collected at the bottom in a "bouquet". In appearance, it resembles cauliflower. The color of the formation can be from light brown to almost black. Often, bristly hairs are visible on its surface. Its size increases very slowly and gradually in accordance with the growth of the body of its owner.

Intradermal papillomatous nevus likes to be located on the back of the neck, under the hair on the scalp, on the face, however, it is also found on other parts of the body. There may be several or one such formation. It develops in accordance with the stages characteristic of epidermal nevi of a different form, and in principle does not differ from them. It is just that the papillomatous growth rises strongly above the surface of the skin and is easily injured, therefore such moles, especially large ones, are recommended to be removed for preventive purposes.

Papillary epidermal nevus - this name indicates that the skin pattern is clearly visible on its surface. This is a favorable sign, since the disappearance of papillary lines on the surface of the mole indicates, at a minimum, the resumption of borderline activity and is an alarming symptom.

Blue nevus is epidermal. Its deep location in the dermis is the reason for the blue or blue tint of the formation. The surface of the blue nevus rises above the skin level in the form of a dome with a diameter of 5 to 20 mm. The bulge is clearly defined, smooth, without vegetation. Most often, blue nevus is located on the skin of the face, arms, legs or buttocks. In the mechanism of development of this formation, two directions are distinguished: the predominance of fibrosis or active division of melanocytes. In the first case, the process indicates its regression (simple blue nevus), in the second, biological activity suggests the possibility of malignant degeneration (cellular blue nevus).

Complications and consequences

A mature epidermal nevus may not manifest itself in any way or spontaneously regress. Such involution is a feature of this particular type of nevi.

The most dangerous complication, although quite rare, is its malignancy. This process is associated with the resumption of borderline activity, the clinical manifestations of which are any of the following:

• a person begins to feel tension, slight tingling, regular itching, and soreness in the area where the nevus is located;
• noticeable increase in the size of the formation;
• the appearance of asymmetry, redness of the adjacent skin, compaction, growths, cracks, ulcers, pain and bleeding;
• change in color or its intensity;
• disappearance of papillary lines;
• hair loss.

Such symptoms do not necessarily indicate a neoplastic process. They may be the result of trauma, inflammation of the hair follicle, thrombosis of the skin vessels, or the development of an epidermal cyst. The consequences of an inflammatory process or trauma usually pass within a week or a decade, so the dynamics of changes in the activated nevus are monitored (for example, a series of its photographs are taken in dynamics), sometimes other diagnostic measures are required.

In addition, in the place of localization of the nevus, under it or nearby, other formations can develop - angioma, the already mentioned cyst, basalioma, melanoma. In the zone of nevus growth, there may be a vascular layer of the dermis, which will cause circulatory disorders, fatty tissue - lipomatosis and other secondary manifestations.

Diagnostics epidermal nevus

Various methods are currently used to determine the benignity of a neoplasm. Firstly, visual signs are assessed: the shape of the neoplasm; its size, and most importantly, its rapid, visible changes; color intensity and uniformity of coloring; clarity of boundaries; symmetry.

Epidermal nevi with signs of renewed activity, dark brown and black in color (especially in patients with a light phenotype), with uneven zigzag borders, and an asymmetrical shape are suspected of malignancy. The presence of colored areas on the surface of the nevus: bluish, reddish, white, black dots, raises concern.

However, such changes may be caused not only by the emerging neoplastic process, but by factors unrelated to it. This often occurs during hormonal imbalances – glucocorticosteroid therapy, during adolescence, in pregnant women. Other factors may be present – intense insolation, professional risks: regular ionizing or electromagnetic radiation, fluorescent lighting, exposure to chemicals. One of the signs of the influence of external factors is a change in all nevi exposed to the effect. Transformations of one mole should cause particular concern.

When removing a mole, histopathological analyses are mandatory, allowing to evaluate changes in the cellular structure and the degree of maturity of nevus cells. The accuracy of histological diagnostics of the structure of skin tumors increases with the use of computer ploidometry.

If unnecessary surgical intervention is desired, a smear from the surface of a suspicious nevus can be taken and examined under a microscope. Sometimes a biopsy of a nearby healthy area of skin is performed. Biopsy material can be analyzed with greater accuracy using infrared spectroscopy or confocal laser microscopy.

A non-invasive method is serial photography of the elements of a changing mole and image analysis using a computer program (comparing them by certain features with an existing database). Other modern instrumental diagnostics are also used, for example, sonographic visualization of pigmented formations using high-frequency ultrasound.

Spectral optical coherence tomography has found application in the diagnosis of melanocytic nevi.

The main method remains dermatoscopy, both classical and epiluminescent, with the help of which it is possible to study an epidermal nevus in an immersion medium, providing a 10-fold increase in its size and image brightness. And computer processing and analysis of a series of digital photographs of a nevus increases the accuracy of diagnosis and allows to avoid unjustified removal of the formation.

Differential diagnosis

Differential diagnostics of epidermal pigmented nevus is carried out with juvenile formation, which differs in the degree of maturity of nevus cells. Cytological examination shows the absence of type C cells (spindle-shaped), atrophic changes, fibrosis, and circulatory disorders.

It is also differentiated from vulgar warts, histiocytoma, hair follicle tumor - trichoepithelioma, cystic basalioma, molluscum contagiosum, neurofibroma, other neoplasms and, of course, melanoma, based on visual differences (FIGARO rule - shape, rapid change in size, "jagged" borders, asymmetry, size ˃ 6 mm, multi-colored coloring), as well as cytology (cellular anaplasia), the presence of a reaction of free stromal cells and features of other morphological manifestations, in particular - the absence of immune mechanisms of spontaneous regression.

Epidermal nevus is differentiated from vulgar warts in patients with immunodeficiency, actinic precancerous hyperkeratosis, acanthosis nigricans, and warty psoriasis. In vulgar warts, in addition to vacuolization of epitheliopites, intra- and extracellular viral inclusions are observed on the border of the spinous and granular layers, the type of which can be determined by in situ hybridization, parakeratosis, and warty dyskeratosis.

In actinic precancerous hyperkeratosis, suprabasal acantholysis, atypical cells, and a mild inflammatory reaction are observed.

In acanthosis nigricans, the lesion is localized in the intertriginous areas; the histological picture is characterized by acanthosis and pronounced hyperpigmentation of the cells of the basal layer.

Differential diagnosis of inflammatory nevus with warty psoriasis is in some cases so difficult that sometimes these conditions are identified

Treatment epidermal nevus

An intradermal pigmented nevus that does not show dangerous symptoms of reactivation, is not subject to regular trauma and is not a cosmetic defect, does not require treatment. In all other cases, it is recommended to remove the disturbing formation by an oncodermatologist with subsequent histological examination of samples of the removed nevus.

Conservative treatment of epidermal nevus with medications is usually not carried out, since such tactics can lead to tragic consequences. Melanoma in the early stages can easily be confused with a benign epidermal formation in appearance. No sensible doctor will recommend medications for external use to get rid of a mole, even if it seems quite safe and benign.

Pharmacies and the Internet offer many different drugs that can eliminate cosmetic defects - growths on the skin, including moles. They can be purchased without a prescription from a doctor. However, such treatment is strictly not recommended, since there is a serious risk that the mole will not be benign at all. And the mechanism of action of drugs for removing moles is based on the chemical layer-by-layer destruction of the formation, so as a result of treatment with such drugs, you can create big problems for yourself. In addition, it is unlikely that external agents intended for softening and removing the stratum corneum of the epidermis will be effective in our case, when the nevus grows from the dermis.

For example, Stefalin ointment, distributed on the Internet, is positioned as an effective remedy for removing skin neoplasms, created exclusively on a plant basis. The drugstore sells an alcohol concentrate of celandine extract, called Mountain Celandine. It also contains plants, in addition to celandine, it contains extracts of gentian, string, golden rhododendron and goose foot. The instructions indicate that the solution is intended for removing warts and papillomas, there is no mention of moles. More effective is the Superchistotel solution, packaged in a small bottle with an applicator. It does not contain any plant components, the active ingredient is a mixture of alkalis, the mechanism of action is based on the keratolytic effect of alkali burns. Skin cells that come into contact with the product die, a crust appears on the upper part of the neoplasm, which will fall off over time. The intradermal nevus is located in the deepest layer. In the best case, such treatment will leave a scar; in the worst case, if the mole had altered cells, it can give impetus to the rapid development of a malignant process.

Of the pharmaceutical preparations for removing nevi, only Solcoderm solution is used. And even then, if you carefully read the instructions, you can understand that only benign formations are removed with its help, therefore, preliminary diagnostics are necessary. And the solution itself is intended for use by medical specialists.

Vitamins and physiotherapy are also usually not used for complaints of discomfort in the area of the epidermal nevus. Vitamin and mineral preparations can be prescribed for general strengthening of the body, physiotherapy can contribute to more effective healing of the skin after mole removal surgery. But any impact on the mole for therapeutic purposes is not welcomed, as it can be dangerous.

Folk treatment is also not an option. Official medicine has not found confirmation of its effectiveness. In the best case, a mole growing from the dermis layer will not go away, even if it is regularly steamed, cauterized with garlic paste or vinegar essence, and then the top layer is scraped off with pumice. Herbal treatment, mainly celandine, is carried out in the same way. Even a benign nevus will not withstand constant mechanical impact and, at a minimum, will become inflamed. And what if the nevus already contains altered cells?

Homeopathy may be able to help. However, there is no official confirmation of this. At least in this case, no mechanical impact on the object of treatment is assumed, so a priori a benign nevus may simply remain in place, but in the case of melanoma, lost time may turn into a disaster.

The only real method to date for getting rid of epidermal nevus is surgical treatment. Moreover, preference for removing melanocytic nevi is given to classical surgery - the mole is removed with a scalpel with a small area of the surrounding tissue, followed by examination of samples of the removed tissue to exclude neoplastic changes in nevus cells. This is especially true for large and giant nevi.

If the mole does not grow hair and is not too large, then the so-called razor excision can be used. This procedure is less traumatic, the surgical site heals faster and does not leave a scar, and the possibility of examination is preserved.

Surgical treatment of epidermal nevus is not performed on pregnant women, people with mental pathologies, during acute and exacerbation periods of chronic diseases, in the presence of oncological pathologies, decompensated diseases of the cardiovascular system and autoimmune spectrum.

In clinics equipped with modern equipment, laser and/or radio wave knife removal methods can be offered.

The laser knife cuts off the neoplasm layer by layer down to healthy skin. The operation is bloodless, highly precise and relatively painless. There is no direct contact with the instrument and, accordingly, no risk of infection. Unlike evaporation with a laser beam, the material is preserved for subsequent examination, therefore, when removing melanoma-hazardous nevi, a knife is used, although with this method there is a risk of getting a burn during the procedure.

Laser evaporation leaves no material for examination, this method is highly accurate and safe, it is good to use for removing moles located in open or hard-to-reach areas of the body. However, it is used only in cases where the benign nature of the nevus is beyond doubt.

The radio wave knife leaves the possibility of examining a remote object. The operation performed with its help is painless, low-traumatic, safe and highly accurate. After it, damaged areas of the skin are quickly restored, and healthy ones are not injured. With the help of a radio wave knife, melanoma-dangerous neoplasms are also removed, except for especially large and giant ones. This method is not suitable for patients with a pacemaker, as well as the contraindications listed above.

After the operation to remove epidermal nevi, it is necessary to follow certain precautions recommended by the doctor: protect the postoperative surface from damage, if necessary, do antiseptic treatment and apply a bandage, do not expose it to prolonged insolation, do not swim in natural and artificial reservoirs. If you find any changes in the area of the removed neoplasm, for example, in the density or color of the skin, you must immediately consult a doctor.

Prevention

It is unlikely that it is possible to influence the number and location of moles on the body, since this is genetically determined.

Therefore, one can only try to avoid their malignant transformation, not exposing the body to excessive radiation and trying not to injure nevi. Formations located in places of constant pressure or friction are best removed immediately.

It is recommended to perform planned removal operations during the period of greatest hormonal stability: before puberty or in adulthood, as well as during the period of lowest solar radiation intensity – late autumn or winter.

Maintaining general health and a strong immune system will also be a reliable preventative measure.

If an epidermal nevus is accidentally damaged or clinical symptoms of renewed activity appear, it is necessary to consult a doctor of the appropriate specialty without delay.

Forecast

Acquired epidermal nevus is the most common type of mole and in the vast majority of cases does not pose any danger to life or health.

Congenital formations, especially large and giant ones, require increased attention, since their cells are much more likely to degenerate.