Melanocytic nevus

A melanocytic nevus (Latin: naevus melanocyticus) is a benign pigmented lesion of the skin that occurs due to the localized accumulation of melanocytes – the cells that produce melanin. It can be either congenital or acquired and is found in the majority of the population. These lesions vary in size, color, and location, and typically appear as spots, papules, or nodules with a coloring ranging from light brown to dark brown. Although in the majority of cases they are benign, they require regular dermatological monitoring because some may undergo malignant transformation towards melanoma.

Nevus melanocytic - what is it

A melanocytic nevus results from the proliferation (excessive multiplication) of melanocytes within the epidermis, dermis, or both layers simultaneously. Under normal conditions, melanocytes are evenly distributed in the basal layer of the epidermis. In nevi, they form clusters known as melanocytic nests.

The formation of nevi is contributed to by:

genetic predispositions,
exposure to UV radiation,
hormonal changes (puberty, pregnancy),
phenotypic predisposition (fair complexion, skin phototype I-II).

Nevi are classified as:

congenital – present from birth or appearing in the first months of life,
acquired – developing over the course of life, most commonly in childhood and adolescence.

The clinical characteristics of a typical nevus include:

symmetrical shape,
regular, well-defined borders,
uniform coloration,
diameter usually <6 mm,
stability over time.

Any deviation from these characteristics requires in-depth dermatoscopic diagnostics.

Melanocytic nevus - types

The classification of melanocytic nevi is based on their histological location (i.e., the placement of cells within the structure of the skin) and clinical appearance.

Histological classification:

Junctional nevus
- melanocytes are located at the dermo-epidermal junction,
- usually flat, dark, with clear borders.
Compound nevus
- cells are present in both the epidermis and the dermis,
- the lesion is slightly raised, often with varied pigmentation.
Intradermal nevus
- melanocytes are located exclusively in the dermis,
- usually dome-shaped, light brown or skin-colored, often hairy.

Other significant clinical types:

Atypical (dysplastic) nevus – with irregular borders, heterogeneous color, and an increased potential for malignant transformation.
Giant congenital nevus – with a large surface area, associated with a higher risk of melanoma.
Spitz nevus – often occurs in children, can clinically resemble melanoma, requires differential diagnosis.
Blue nevus – with a bluish tint due to the deep location of melanocytes.

Diagnosis is based on:

dermoscopic examination,
photographic documentation,
in selected cases – histopathological examination after excision of the lesion.

Melanocytic nevus – is it treatable?

A melanocytic nevus, as a benign lesion, does not require treatment if it does not show atypical features or cause discomfort. Management depends on medical or aesthetic indications.

Indications for nevus removal:

suspected malignant transformation (the lesion meets ABCDE criteria: asymmetry, irregular borders, color variation, diameter >6 mm, evolution),
mechanical injuries (e.g., in areas prone to irritation),
rapid growth or structural change,
aesthetic reasons.

Removal methods:

Surgical excision with tissue margin - the method of choice for oncologically suspicious lesions; the material is sent for histopathological examination.
Laser therapy - used only for clearly benign pigmented lesions, after prior dermatological assessment.
Electrosurgery or radiosurgery - in selected cases of superficial lesions.

It should be emphasized that:

every pigmented lesion should be dermoscopically evaluated before removal,
removing nevi without prior diagnosis may hinder melanoma detection,
self-attempts to remove lesions at home are contraindicated.

Prevention and monitoring

annual dermoscopic examination by a dermatologist,
self-examination of the skin every 1–2 months,
sun protection (SPF 30–50, avoiding peak hour exposure),
avoiding tanning beds.

Early detection of melanoma significantly increases the cure rate, which is why regular monitoring of nevi is an element of oncological prevention.