Nevus - Causes, symptoms and treatment. MF.

Nevus( from the Latin naevus), or nevoid tumor, birthmark, birthmark is a developmental defect that is characterized by the appearance on the skin, less often on the mucous membranes, conjunctiva( thin transparent tissue covering the eye from the outside) and in the vascular( middle) shell of the eyeball(iris and choroida) of spots or formations consisting of so-called nevus cells.

Non-viral cells appear during fetal development from the neural crest - a special set of cells from which a variety of anatomical formations develop( nerve nodes, meninges, some adrenal cells, and skin pigment cells( melonocytes)).Due to some insufficiently studied reasons, non-viable cells do not reach the maturity of melanocyte. Melanocyte precursors( melanoblasts) migrate into the deep layer of the epidermis( the epidermis is the outer layer of the human skin, represented by multilayer epithelium), but some of them do not reach it, but remain in the dermis( connective tissue part of the skin located under the epidermis).

Nevus is normal

Nevuses are found in 75% of the representatives of the Caucasoid race. On the body of an adult there is an average of about 20 nevi, but in some people their number may exceed 100. In childhood, the nevus may remain invisible, but during the period of puberty, under the influence of sunlight, and during pregnancy, the manifestation of nevi is possible.

In its development, the nevus undergoes several phases: the nevus is first intraepithelial, then transformed into a borderline, and at the age of over 30 years passes into the phase of the intradermal. With the onset of the elderly, the nevus often undergoes a reverse development: the nevus cells are immersed inside the dermis and undergo changes, eventually replaced by a connective tissue. This evolution of the nevus is associated with the stages of simplification of the organization and functions of melanocytes: melanocyte - an unprimed cell - fibrous( coarse connective) tissue.

The vast majority of nevi are acquired, which are divided into ordinary and special types. Among ordinary nevi, in turn, distinguish borderline, complex( epidermo-dermal) and intradermal forms.

Border, or junctional, nevus appears, as a rule, in the first two decades of life and is located mainly on the skin of the face, neck, trunk, hands, in some cases, and on the external genitalia;shows a uniformly pigmented( from light brown to dark brown) stain with a diameter of 1-5 mm, maximum to 10 mm, having a round or oval shape, a smooth surface and clear boundaries. The surface of the border nevus is devoid of hair. This form of nevus exists until about the age of 35 years.

Mixed, or complex, nevus is a transitional form from the borderline to the intradermal nevus. It can be predominantly borderline or predominantly intradermal. The mixed nevus has a spherical shape and a dense consistency, its color can vary from light brown to black, the dimensions, as a rule, do not exceed 10 mm.

Intradermal nevi is more common in mature or advanced age. It can be single or multiple, and is located primarily on the face, neck or trunk. The intra-dermal nevus has the appearance of a domed or warty formation, which in shape may resemble a blackberry berry and have a "leg".Its dimensions vary from 2 mm to several centimeters, color - from pale brown to black, but sometimes there is a depigmented( pigmentless) intradermal nevus of whitish or pink-red coloration.

From the localization of conventional nevi in ​​different parts of the body and the peculiarities of the location of nevus cells in them, their external manifestations depend: on the palms and soles, where the stratum corneum has a large thickness, complex and intradermal nevi do not protrude above the skin level. Elevated above the level of the skin, nevi are characterized by a pronounced intradermal nevus component, and flat ones by a borderline component. The stronger the nevus appears above the level of the skin, the weaker it is pigmented.

Conventional nevi grow in size in direct proportion to the growth of the human body. Their number increases after birth and reaches the maximum number during puberty, and after 50 years it gradually decreases, and by 70-90 years they, as a rule, completely disappear.

Congenital nevias of are benign pigmentary tumors, which consist of nevus cells( melanoblast derivatives) that result from a violation of the melanoblast specialization process during the intrauterine period. Congenital nevi are present in 1% of the children of the Caucasoid race and can be detected at birth or during the first year of life of the child. They come in different sizes, even giant ones. Congenital nevuses are light brown or dark brown, somewhat protruding above the skin, sometimes they can be covered with hair, although hair growth does not start immediately. Congenital nevuses have a round or oval shape, clear or blurred borders, the right or wrong shape. Their surface can be with a preserved skin pattern or tuberous, wrinkled, folded, lobed, sometimes covered with papillae resembling brain convolutions. They can be located on any part of the skin. In 5% of cases, these nevi are multiple, but then one of them is larger. Larger nevuses are soft to the touch. Congenital nevi are almost indistinguishable in appearance from the acquired nevi, the only external difference is the diameter of more than 1.5 cm( acquired nevuses of such sizes do not reach).Large( more than 20 cm in diameter) and giant congenital nevuses occupy part of the anatomical region or all of it( trunk, limb, head or neck), but in combination with multiple small congenital nevi. Small congenital nevuses in 95% of cases are single. Another difference between congenital nevi is that the nevus cells are located in the deep layers of the dermis, in the subcutaneous fat, in the appendages of the skin. Congenital nevi, in contrast to acquired nevuses, do not disappear spontaneously.

Congenital nevus of face

A dysplastic nevus ( Clark nevus, an atypical nevus) is an acquired pigmentary lesion formed as a result of a chaotic division of atypical melanocytes. It occurs in 5% of the population, develops on healthy skin or against a complex( mixed) nevus, less often borderline. The dysplastic nevus appears later than the acquired nevus - before the beginning of the puberty period, during life, up to old age, is usually located on the trunk and extremities. The development is facilitated by being under the sun's rays. Spontaneous disappearance for a dysplastic nevus is not characteristic. The dysplastic nevus occupies an intermediate position between the acquired nevus and the surface-spreading melanoma. Outwardly it looks like a spot with separate areas rising above the level of the skin, has large dimensions( more than 15 mm in diameter) and uneven coloring, which can be motley, like fried eggs or a target. Also asymmetry and irregular boundaries, fuzzy, uneven edges are characteristic.

Dysplastic nevus

Risk of malignancy( malignancy) of nevi.

The very presence of a nevi in ​​a person creates a certain risk of developing a melanoma of the skin - a malignant tumor that develops from melanocytes. In people with multiple small nevi, this risk is greater than the average. The risk factor is not only the number of nevi on the skin, but also the presence of their forms protruding above the surface. The occurrence of skin melanoma is possible after a trauma of the nevus: a single( bruises, abrasions, cuts) or chronic( permanent trauma with clothing or shoes).

Since in 50% of cases of skin melanoma develops against the background of nevuses, they are treated as a precancerous disease. There is a direct relationship between the size of nevi and the frequency of their malignancy.

With regard to malignancy, there are two most dangerous types of nevi: dysplastic and congenital. Under certain conditions, dysplastic nevi can be regenerated in melanoma in 100% of cases. In any of the congenital nevi can also develop melanoma.

The risk of malignancy of a nevus with a diameter of more than 2 cm is 5-20%, with a special danger posed by nevuses located on the face. In a person who has 20 nevi, the risk of melanoma increases by 3 times.

The main external differences of melanoma( 4 photos to the left) from nevi( 4 pictures on the right), from top to bottom: asymmetry, uneven contours( torn, dentate border), uneven pigmentation( coloration of various shades of black and brown), change in the diameter of the element.

Tactics of treatment, indications for surgical removal of nevi.

In most cases, the acquired nevi do not require any treatment, but there are indications for their surgical removal:

1. Cosmetic indications( at the patient's request to remove the disfiguring nevus).
2. The location of the usual nevus in difficult for self-control places( for example, on the scalp, perineum).
3. Identification of such signs of atypia in the nevus as a non-uniform distribution of melanin, serration of its borders, their indistinctness, relatively large diameter( more than 5 mm).
4. Atypical development of the nevus, including a sudden change in shape and size.
5. Nevus with a high risk of malignancy( eg, a giant congenital nevus, dysplastic nevi).All small congenital nevi that have an unusual appearance( uneven color, irregular shape, etc.) should be surgically removed before the patient reaches the age of 12 years. The operation to remove the giant congenital nevus is carried out as soon as possible.
6. With the preventive purpose in some cases, it is advisable to remove the nevus with a significant amount, as this prevents the occurrence of melanoma.
7. Intensively colored nevuses of the peripheral location in the limb, mucosa, subungual and conjunctiva regions: they should be removed, since the possibility of dysplastic nevi of such a localization causes caution with regard to their degeneration into melanoma.
8. Frequent re-irritation and trauma to a nevus, such as under a belt, bra or collar.

Clearly defined and indications for immediate excision of the nevus. They are signs of its sudden change during the last month or several:

1. Increase the area and height of the nevus.
2. Increase in the intensity of pigmentation, especially when it is uneven.
3. The appearance of the corolla from the pigment around the nevus, the appearance of satellite elements.
4. Inflammatory process in the nevus.
5. Appearance of itching.
6. Formation of erosion and the appearance of bleeding.

Removal of nevus

Removal of nevi should be performed by an oncologist, be radical and performed only by surgical method with mandatory subsequent histological examination of the removed tissues. Partial removal of the nevus is unacceptable, since after that the nevus repigments and recurs, forming a pseudomelanoi. Cosmetic outcome is often unpredictable in this case, such treatment can lead to the development of a relapse with consequences less favorable than before the beginning of treatment.
Such methods of removal as electrocoagulation, cryodestruction, dermabrasion, laser removal with nevi skin and mucous membranes should not be used, as they make it impossible for histological confirmation of the diagnosis.

The removal of small nevuses in adults is possible under local anesthesia and is considered a relatively simple surgical procedure that does not require any preliminary preparation from the patient. After excision of the nevus, the seams that form on the skin are superimposed on the edges of the defect formed on the skin, a sterile dressing is fastened on top for a few days, dressings are made every day for a week, after the wound is healed, the seams are removed. In detail, the process of removing a nevus with photos during an operation is discussed in the article "moles, birthmarks" & gt; & gt;

In operations with large nevuses, when extensive skin defects are formed, they are resorted to by skin plasty to close them, and surgical intervention is performed under general anesthesia.

All surgical interventions in children are performed only under general anesthesia.

Prophylaxis of malignancy of nevi

Prevention of melanoma in patients with nevi is the early and active detection of subject matter forms( primarily dysplastic nevus).It is necessary to allocate patients with the presence of these forms in the "risk group" and conduct a constant dynamic monitoring of the changes in these elements, or delete them.

Patients with dysplastic nevi should be aware of the signs of the degeneration of these nevuses in melanoma and thus independently regularly monitor the nature of their changes. These patients are advised to avoid exposure to the sun, and when leaving the street to apply sunscreen.

Doctor surgeon Kletkin ME