Nevus: types, classification and causes development

Nevi or moles are congenital or acquired
benign lesions on the skin, which consist of clusters
melanocytes. In other words, nevi are moles or birthmarks.
the spots that exist on each person’s body and are
malformation of skin cells. The term “nevus” is derived from
The Latin word for “naevus”, which means “mole”. Normal nevi –
a very common phenomenon that does not require treatment and does not
poses a threat to human health. However, there are
some types of nevi that are highly likely to
reincarnation in malignant disease.

Moreover, nevi are not always congenital pathologies, very
they often appear during life on the human body. Usually
before the age of majority, the number and size of nevi can
increase and gradually decrease over time. This fact
due to the fact that nevi grow simultaneously with the body, and
when maturation ends, nevi also stop growing.


  • Causes of development
  • Types and classification of nevi
  • Diagnosis of nevi
  • Treatment of nevi
  • Prognosis and prevention

Causes of development

The reasons for the development of nevi lie in violation of the migration process
melanoblasts (melanocyte progenitor cells). Eventually
melanoblasts form a significant concentration, from which later
nevi are formed. Nevi are divided into congenital and acquired,
but many experts are inclined to believe that this classification
very conditional. Since the nevi that appear in adults
people, it is not newly formed, but inborn, manifested with
over time.

Thus, it is possible to identify the main causes contributing to
the formation of nevi in ​​the womb:

  • acute infectious diseases of the genitourinary system
    a pregnant woman;
  • exposure to toxic-allergenic agents;
  • exposure to ionizing and radiation exposure;
  • pathologies accompanying pregnancy (the threat of miscarriage,
  • hereditary factor.

Reasons that can trigger the development of acquired

  • hormonal surges during puberty;
  • taking contraceptives;
  • mechanical skin lesions;
  • allergic skin diseases;
  • skin infections;
  • pregnancy, during which hormonal
  • exposure to ultraviolet radiation on the skin.

Types and classification of nevi

At the same time, congenital and acquired nevi can be
similar in structure. For this reason, it is appropriate to classify
nevi on the histological structure. This classification allows
take into account the main features of each nevus and allows with a large
probability to predict their further development. Exists
more than 50 types of moles, of which the most common
about 10 species. All nevi are divided into two types:

  • melanoma;
  • melanohazardous.

Melanomonevirus nevi almost never malignant,
therefore, recommendations for their removal are purely cosmetic

Melanoma-dangerous nevi pose a great danger of development.
malignant disease. Education data is almost always

By molonomonasny moles include:

  • Mongolian spot;
  • papillomatous nevus;
  • fibroepithelial nevus;
  • halonevus;
  • intradermal pigment nevus.

Mongolian spot is a congenital nevus, which is observed
most often in newborns of the Mongoloid race. This type of nevus
its essence is a genetic variant of the disruption process
skin pigmentation. This type of nevus disappears in most
children to the age of five. This pathology is localized on
buttocks and sacrum. There are cases when the Mongolian spot is not
disappears altogether, and so it remains for life, but even in this
case there is no medical evidence of their rebirth
malignant disease. Data nevi in ​​the treatment is not


Papillomatous nevus has a very unsightly appearance that
very frightened by its owners. Therefore, people with this type of nevus
often turn to an oncologist, suspecting the development of the worst
script. Papillomatous nevi significantly rise above the skin,
differ in shape and color from the rest of the skin. Surface nevus
It has a brownish surface. This nevus is not
causes subjective sensations, in addition to psychological discomfort
(when a nevus is located on the face, neck, hands). Beloved
localization of papillomatous nevus scalp, on
trunk or limbs. Papillomatous nevi change their
characteristics throughout life, they can grow in size,
change its color but degenerate into a malignant formation


Fibroepithelial nevus is the most common type of mole.
This type of nevi can be both congenital and acquired.
They very often appear in the period of hormonal changes,
occurring in the body. But in medicine, there are cases
when such nevi appeared in old age. Usually
fibroepithelial nevus is round, pink in color and
elastic consistency. Birthmark grows for some time, but on
a certain stage, its growth slows down, after which it is no longer
is progressing. Rebirth of fibroepithelium nevus happens

Galonevus or Nevus Settona is an acquired mole, which
develops in people with reduced immunity, autoimmune
diseases, as well as disruptions in the hormonal system.
This pathology triggers an autoimmune reaction that fights against
own body cells. Galonevus is characterized by round
or an oval shape that slightly rises above the surface
skin. The form of this nevus is consonant with its name. central part
nevus has a more intense color, and its edges – less
intensive. It resembles an optical phenomenon – a halo, which
formed around the sun or moon. Main center
the haloneus is surrounded by a pale halo. Localized halonevus
on the body, limbs, less often – on the face, mucous membranes,
feet and soles. Galonevuses are not recommended to be removed, as they
may be symptoms of more serious internal pathologies.
The rebirth of halonevus in skin cancer occurs very rarely.


Intradermal pigment nevus usually appears in
puberty period. At the beginning of the development of a neoplasm
is located inside the skin and does not protrude above its surface.
Initially, intradermal pigmented nevi are
small in size, but can change during life: change
its color and shape. This type of nevus is not prone to progression.
in old age, as often happens with other types of nevi. Rebirth
intradermal pigment nevi rarely happens.


The group of melano-dangerous nevi includes the following relatives

  • border pigment nevus;
  • dysplastic nevus;
  • nevus otta;
  • giant pigment nevus;
  • blue nevus.

Border pigment nevus in most cases congenital
neoplasm, but in some cases it appears in the early years
child’s life. Usually borderline pigment nevus grows
in proportion to the growth of the body. With increased growth, a nevus can
greatly increase in size. Pigmented nevus slightly
rises above the surface of the skin and contains high concentrations
melanin. This causes the dark color of the mole, which can be
dark brown, dark purple and even black. Pigment nevus
there is no clear localization, it can appear anywhere, but only
This type of mole is found on the palms and feet. Dense
the consistency of a nevus may indicate its malignancy.


Dysplastic nevus is both congenital and
acquired. In many patients, this type of moles appears in
puberty and has a family character, since birthmarks
this type is often diagnosed in two or more representatives
one family. Most often, dysplastic nevi are located on
upper back, legs, thighs, large folds (inguinal,
axillary). As a rule, several
dysplastic nevi, but there are also single rashes. Data
Moles have a variety of colors: they can be like
light brown, and dark brown, or black. Highly
there is often a peculiar color both in the center of the spot and in
its periphery. Dysplastic nevus practically does not rise above
skin, and its surface is flat and smooth. For accurate diagnosis
This mole is given a biopsy that shows typical
accumulation of cells for this type of nevus. Unfortunately,
dysplastic nevus in 90% of cases becomes malignant
the disease, namely melanoma. Therefore, quite often
dysplastic nevus undergoes a radical removal and requires
appropriate treatment.


Nevus Ota is characterized by the fact that it contains a large number
melanin. Most often it is a single element, but there are also
multiple formations that tend to merge. This
the type of nevus belongs to the neurocutaneous group of nevi when
factors. Nevus Ota is localized only on the face: on the cheekbones and along the edge
eye sockets. It appears as a blue-black spot on the eye protein.
or in the cornea area and is characterized by the fact that they change
mucous membrane of the eyes. Especially when a nevus gets big

This type of nevus has a genetic etiology and is
congenital phenomenon. It is found only among representatives of the Asian
races and their descendants. Most often observed in the Japanese and the Mongols,
less often – from the Chinese and other representatives of Asia. Transformation into
malignant disease does not occur often, but still has
a place. Large role in the rebirth of nevus Ota plays
ultraviolet radiation.


Giant pigment nevus is a congenital formation and
noticeable, unlike other congenital nevi, from the first days
child’s life. Nevus progresses as the body grows and
reaches the big sizes. Very often, a nevus is not
just on a large area of ​​skin, and it takes a whole anatomical
an area, for example, a half-face, neck, torso, etc.
when the size of a giant pigment nevus was 35-40 cm. In this
case, we can talk about a pronounced cosmetic defect, since
a giant nevus protrudes above the surface of the skin and is treated as
massive tumor that worsens the appearance of a person. In most
In cases of color, this nevus varies from gray to dark brown.
colors. Giant nevus is characterized by a diverse structure.
So, for example, deep cracks are observed on its surface,
enhanced hair growth, furrows and small warts. All these
Characteristics distinguish giant pigment nevus from other species.

The treatment of this nevus is carried out for aesthetic purposes.
Ozlokachestvlenie giant nevus rarely happens. Sometimes it
occurs after its removal, but experts say that
the formation of such large sizes is more often injured as
contributes to its malignancy. Nevus removal is performed
surgical excision of the tumor and skin grafting (in the case of
large education).


Blue nevus belongs to benign tumors, although
is a variant of the precancerous condition. The color of this nevus
determines its name. In fact, moles are not only
blue, but also blue, dark blue, gray, dark purple or
black color. This type of mole consists of a large cluster
melanocytes that actively produce melanin. More often
blue nevus is a single element, but there are also
multiple rashes. Blue nevus slightly rises above
skin, and when it is palpated there is a dense intradermal node. Have
There is no clear localization of this nevus, it can appear on any
skin area. It has clear boundaries, does not exceed one.
centimeter in diameter and it does not grow hair. More often
the malignancy of a blue nevus occurs after its incomplete
removal or permanent trauma. But the transformation process itself
in malignant disease occurs rarely.


Diagnosis of nevi

The main task in the diagnosis of nevi is their
differentiation with malignant skin diseases, especially with
melanoma. Therefore, the dermatologist-oncologist, first of all, should
eliminate the malignant form of the disease and then tackle
definition and treatment of a nevus. The following are used for this purpose.
diagnostic methods:

  • dermatoscopy;
  • phosphorus isotope diagnostics;
  • thermometry;
  • biopsy;
  • histological examination;
  • echography

Dermatoscopy is performed using a special apparatus, which
magnifies the image several dozen times and allows
notice the slightest changes on the surface of the nevus. Presently
This method is considered the most effective for early diagnosis.
melanomas. But dermatoscopy can not be confirmed with certainty or
reject the diagnosis, and can only prompt the next specialist
diagnostic tactics. The method is painless because
is non-contact and does not affect the patient’s skin
any radiation.

Diagnosis of phosphorus isotope is the accumulation
malignant formation of radioactive phosphorus. Need to say,
that phosphorus is a chemical element that is involved
in cell division. In malignant disease, cell division
occurs more intensively and the need for phosphorus increases. For
This is used isotope phosphorus, which is easy to detect when
scanning moles. With melanoma, the labeled phosphorus accumulates
in nevi, which allows us to talk about enhanced cell division and
allows you to confirm the diagnosis with high probability.

Thermometry is a local measurement of skin temperature using
special apparatus. Scientists have found that the formation of any
tumors, both benign and
malignant, accompanied by an increase in local temperature.
This is because the increased metabolism is always
accompanies cell division. During thermometry is measured and
compares the surface temperature of healthy skin and on the surface
neoplasms. Thus, with benign development
the disease temperature fluctuates within one degree, in
case of malignant formation temperature difference
ranges from 2 to 2.5 degrees.

Biopsy is the most reliable method for determining species.
nevus, and also helps to identify at the earliest stages
development of malignant education. Biopsy is a
a piece of tissue (biopsy) from a neoplasm for microscopic
research. The appearance of the cells and their location makes the conclusion
about the pathogenesis of this formation.

Biopsy is of the following types:

  • in the form of a puncture (puncture);
  • excisional (total).

A puncture biopsy is a collection of cells using
injection needle. The cells are taken point and in limited
quantity. This method allows you to correctly put
diagnosis and choose further tactics regarding treatment and
development of the disease.

Total excisional biopsy can be attributed not only to the methods
diagnostics, but also to medical procedures. This method assumes
removal of a neoplasm with its subsequent histological
research. In this case, the diagnosis is the most accurate, since
the tumor itself is being examined. But this diagnostic method is used
only in the case of superficial nevi.

Treatment of nevi

Treatment of nevi is their surgical removal.
Carry out the removal of nevi by medical or aesthetic
indications. Medical indications are cases of reborn nevi
in malignant disease. Aesthetic indications – in case
pronounced cosmetic defect. The following methods exist.
moles removal:

  • laser surgery;
  • cryodestruction;
  • electrocoagulation;
  • surgical excision.

Laser removal is the most common way.
remove nevi. Nevus tissues are evaporated with a carbon dioxide laser,
leading to cell death. The method is painless, the patient
only feels a slight burning sensation and warmth. After removing the laser does not
scar or scar remains. Of great importance is the size of a nevus and
its location in the tissues. When the surface location of the nevus
incomplete evaporation occurs, which can lead to

Cryodestruction is the removal of moles using liquid nitrogen.
This method is carried out with small moles that have
superficial location because incomplete removal of moles
promotes its re-development. The method is painless to
after it, scars and scars do not remain.

In the course of electrocoagulation, tissues are also evaporated.
neoplasms only under the influence of electric current.
Use this method to remove small nevi.

Surgical excision is performed using traditional
scalpel. The surgeon removes the tumor as well as nearby tissues. After
removal of a mole stitches, and in its place a scar is formed.
The operation is performed under local anesthesia.

Prognosis and prevention

The prognosis of the disease is favorable, but it should be independently
to monitor melano-dangerous nevi. Also
regularly observed by an oncologist. Nevi Prevention
there is, but there is prevention of skin cancer. She is in
The following events:

  • avoid exposure to direct sunlight
  • is in the sun at a safe time: until 11-00 o’clock in the morning and
    after 17-00;
  • protect your skin with high sunscreen
    SPF protection factor of at least 30;
  • use natural sun protection: shade from trees,
    light, light-colored clothing covering large areas of skin;
  • do not forget to wear hats, Panamas and sunglasses;
  • use products that contain beta-carotene,
    which help the body produce melanin;
  • use as much as possible moisturizing creams, because
    the sun’s rays contribute to the dehydration of the skin, and therefore,
  • protect the skin from mechanical injury, permanent injury
    nevi can lead to skin cancer;
  • protect the skin from the effects of carcinogens. Contact with household
    chemical means can cause cell mutagenesis.

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