Melanocytic nevus


What is a nevus?

Nevi are very common skin changes.

The correct name is melanocytic nevus because it arises from a proliferation of melanocytes, the cells that provide pigment or color.

It can be called pigment nevus if it

  • brown
  • black
  • or colored.

The nevus is a benign (harmless) formation, but it can develop into melanoma (malignant nevus).
Nevi can arise from other skin cells (for example, vascular nevi are malformations of blood vessels), but only those derived from melanocytes are called nevi.

What do nevi look like?

Nevi can:

  • sublime or
  • be flat.

They vary in color:

  • From pink to skin tones
  • too dark brown or black.

Even though they usually have a round or oval shape, they sometimes have an unusual appearance.
They are of different sizes:

  • of a few millimeters
  • up to a few centimeters.

The number of nevi a person has depends on:

  • genetic factors,
  • exposure to sunlight.

People with an increased number of nevi have a greater risk of developing melanoma compared to those who have few nevi.

When do nevi occur?

  • One or more nevi may be present at birth (congenital).
  • They occur most often during childhood and adolescence, and in this case are called acquired.
  • The number of nevi is increased by:

Types of melanocytic nevi

The conventional classification of melanocytic nevi depends on the following factors:

  1. from the microscopic aspect (dermatopathology);
  2. from the skin area in which they form;
  3. of its depth.

Junctional nevus
The junctional nevi are groups or cell nests on the junction zone of the birthmark between the epidermis (epidermis) and dermis (inner layer). They are:

  • level
  • pigmented
  • benign.

Dermal nevus The cells of the dermal or intradermal nevus
are located in the dermis. These formations are thick and usually protrude above the surface of the skin (papillary nevus).
They are:

  • pigmented
  • or skin colour,
  • benign.

Combined nevus
The combined nevus indicates two different types of nevus within the same skin lesion, including:

  • general nevi,
  • blue nevi,
  • Spitz-Nävi.

Classification according to structural properties

A new classification of melanocytic nevi is based on their appearance in the reflected light microscope, a technique used in dermatology to evaluate the structural elements of moles using a handy magnifying device.

  • Reticular nevus
    Reticular nevi show a grid pattern of brown, intersecting lines.
  • Compound nevus
    In the case of compound nevus, the nevus cells are located junctionally cutaneously-epidermal and also within the dermis.
    These moles have a raised center and may be surrounded by a flat pigment area.
  • Globular nevi
    Globular nevi have an oval and brown clumped structure.
  • Blue nevus
    The blue nevus is a skin change of uniform structure and steel blue or greenish color.
  • Starburst nevus (exploding star)
    Starburst nevi have star-shaped lines along the periphery of the lesion.

Classification by localization

  • Facial nevus
    Facial marks form pseudo-networks around hair follicles.
  • Acral nevus
    The acral nevus occurs on the palms and feet and is formed by parallel lines.

Nevi with special characteristics

Nevi with special characteristics include:

  • nevus with eczema,
  • Nevus Sutton (with Halo).

Unclassifiable nevus
The unclassifiable nevus is not one of the other models.

Types of congenital melanocytic nevi

It is a hyperchromic, since birth (true congenital nevus) or a shortly thereafter formed (similar to the congenital or later acquired) nevus.

Small congenital nevus
The small congenital nevi have a diameter of less than 1.5 cm.

Medium congenital nevus
The middle congenital nevi have a diameter of 1.5 to 20 cm.

Giant nevus
The giant nevus is larger than 20 cm.

Naevus pigmentosus et pilosus Naevus pigmentosus et pilosus
is a birthmark with long and coarse hair growing on it.

Café-au-lait spot
Café-au-lait spots are flat plaques of brown color.

Speckled lentiginous nevus or nevus spilus The nevus spilus
is a flat, brown mark with many dark speckles inside.

Nevus Ota Nevus Ota
is a brown or bluish spot on:

  • Forehead
  • Eye
  • Cheek.

Mongol spot The Mongol spot
is a large, blue nevus that often appears on the buttocks of the newborn.

Types of acquired melanocytic nevi

A nevus that appears after birth can be defined as an acquired mark.
It often is:

  • pink
  • brown
  • or blackish.

Dark-skinned people usually have very dark marks.
The acquired nevus can be divided into:

  • typical
  • or atypical (not typical) .

The typical nevus occurs in almost all people.
The term atypical is used for any anomalous nevus.
However, some dermatologists use the term atypical to describe moles with specific characteristics:

  1. large (> 5 mm);
  2. irregularly limited or poorly defined;
  3. different shades of color;
  4. may be flat or raised;
  5. this type of nevus is also called Clark’s nevus.

Common nevus
An ordinary nevus is a flat mark with a uniform and uniform color.

Atypical nevus People with numerous atypical marks have a greater risk of melanoma (malignant nevus

Dysplastic nevus Dysplastic nevus refers to an atypical nevus
that has certain microscopic characteristics.

Blue nevus
The blue nevus is a type of pigmented nevus sitting in deeper layers of the skin.

Nevus cellularis
The nevus cellularis is a non-pigmented skin nevus.

Miescher nevus
The Miescher nevus is a shiny and dome-shaped skin nevus that often appears on the face.

Unna nevus
The Unna nevus is a papillary skin nevus of the shape of a raspberry.

Meyerson’s nevus Meyerson’s nevus is characterized by halo-eczema/dermatitis.

Sutton nevus The Sutton nevus
has a white courtyard (halo) surrounding it.
This formation disappears over the course of several years.

Spitz nevus The Spitz nevus (also called epithelioid cell nevus
) is pink (classic Spitz) or brown (pigmented Spitz), has a dome-like shape and occurs in children and adolescents. The spitz nevus is a benign tumor.

Reed nevus
The Reed nevus is a spindle cell-shaped, very dark nevus in the middle with striped edges.
Reed’s nevus is benign but difficult to distinguish from melanoma.

Recurrence nevus
The recurrence nevus refers to the reappearance of a pigment in a scar after surgical nevus removal.

Naevus agminatus
Naevus agminatus is a collection of similar nevi or freckles.

Acral nevus Acral nevus refers to a nevus
on the palm or sole of the foot. It can also occur on the scalp.

Ungual nevus An ungual nevus
causes a uniformly pigmented longitudinal band on the fingernail or toenail.

Other types of nevi

nevus anaemicus is characterized by a lighter patch of skin and appears mainly in the chest area.

nevus depigmentosus is a patch of skin characterized by the absence of melanin (hypopigmentation).

white sponge nevus is a light, congenital and benign spot that can affect the mucous membrane in the mouth and genital area.

The fire mark or “port wine stain” is an angioma that presents itself as a purple facial spot.

fibromatous nevus is a benign pigmented malformation (not neoplastic).

hyperkeratotic nevus has an almost round shape and resembles a wart on its surface, the color can range from red to dark brown.

choroidal nevus is an asymptomatic tumor that appears as a pigmented plaque with a round shape or with visible edges.
It can be a simple nevus or melanoma.

An inflammatory linear verrucous epidermal nevus is a striped plaque that looks like psoriasis.
It is composed of papular and eczematous areas that flake.

The sebaceous gland nevus is also called organoid hamartoma because inside it can contain the components of the skin organs:

  1. Sebaceous glands
  2. Hair follicles
  3. Apocrine glands
  4. Connective tissue

It is a benign skin lesion and is a variant of epidermal nevus.
It usually occurs on the scalp, but can also occur on the face, neck and forehead.

When to worry about a more melanocytic nevus?

  • In adults, it is important to pay attention to changes in a nevus.
    Malignant melanoma is a cancerous proliferation of melanocytes (pigment cells).
  • Initially, melanoma may resemble a harmless nevus, but over time its structure becomes disordered, tends to enlarge and can also degenerate ulceratively.
  • If a nevus changes its size, shape, color or develops after the age of 30, it should be examined by a dermatologist or other competent doctor.
  • It is not always possible to classify the skin change as melanoma only by appearance. Therefore, if there are doubts, then removal of the nevus may be necessary to conduct a pathological examination.
  • Sometimes nevi change for other reasons, for example, after sun exposure or during pregnancy. They can enlarge or shrink (disappear).
  • In adolescents, a white spot may form before the onset of disappearance.
    Then it is a Sutton nevus.
  • Melanoma can also develop in the mucous membrane. For example, vulvar melanoma occurs on the vulva, but has the same characteristics as melanoma on the skin.

How is melanocytic nevus diagnosed?

Usually, nevi are clinically diagnosed based on their typical aspect.
The criteria for detecting melanoma at the initial stage are determined by the ABCDE rule.

  • A – Asymmetry: the right side is different from the left.
  • B – Border: irregular.
  • C – Colour: varying degrees of pigmentation, multi-colouredness.
  • D – Diameter – greater than 6 mm.
  • E – Evolution: changes in a few days or weeks.

If there are doubts about the diagnosis, it can be removed for a biopsy, even if the possibility that it is malignant is remote.
A partial biopsy is not recommended, because malignant areas could be overlooked.

Removal of the melanocytic nevus

Although the nevi are mostly harmless, removal can be done in the following cases:

  • Possible malignancy:
    – a nevus that has bled, – has an unusual shape, – grows rapidly,

    – changed its color.
    Such a nevus is sometimes called an “ugly duckling” and can be a melanoma.

  • Complaints: a nevus that is irritated by clothing, when combing or shaving.
  • Aesthetic reasons.

Shave biopsy
To examine a raised nevus, a shave biopsy is performed. In the process, the affected skin region is anesthetized, and the doctor removes the raised part of the nevus with a scalpel or electrosurgically.
The wound heals and leaves a white flat spot, but sometimes the color of the original nevus remains.

Shave biopsy is sometimes used to remove brown, flat plaques or freckles and examine them pathologically.
This procedure is called cauterization or tangential excision.

Excisional biopsy
Excisional biopsy is necessary if the nevus is flat or melanoma is suspected.
The entire layer of skin is removed and then sutured.
For pathological (histological) examination, the tissue sample is sent to a laboratory.
The resulting scar can be a fine line, but sometimes it stands out more clearly than the nevus.
Coarse hairs that sometimes form on the nevus can be removed by:

  • Shaving
  • Electrolysis
  • Laser
  • along with the entire nevus.

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