Junctional nevus
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A junctional nevus (Lat. nevus junctionalis) is one of the types of melanocytic nevi, that is, benign skin lesions that arise from a local accumulation of pigment-producing cells – melanocytes. A characteristic feature of a junctional nevus is its location at the border between the epidermis and the dermis, i.e., at the so-called dermoepidermal junction. These lesions most often appear as flat or slightly raised pigmented macules with an even coloration. They frequently occur in children and young adults, can appear on various areas of the body, and are usually benign in nature. In dermatological diagnostics, however, assessment of their appearance and any changes over time is particularly important, because some melanocytic nevi require monitoring to differentiate them from cutaneous melanoma.
Junctional nevus – what does it look like
The junctional nevus has characteristic morphological features that allow it to be distinguished from other pigmented skin lesions. In clinical and dermatoscopic examination the following are most commonly observed:
- a flat or very slightly elevated skin lesion,
- uniform coloration in shades of light brown, dark brown, or black,
- well-defined borders,
- a smooth surface, without signs of keratinization or scaling.
The diameter of junctional nevi usually ranges from a few millimeters to about 1 cm. These lesions may occur singly or in greater numbers and appear in various locations, such as:
- the face,
- the trunk,
- the extremities,
- the hands and feet.
In dermatoscopic examination a regular pigment network pattern is typical for a junctional nevus, resulting from the distribution of melanocytes within the dermoepidermal junction. In the histopathological picture nests of melanocytes located precisely in this layer of the skin are visible.
It is worth emphasizing that a junctional nevus may, over time, undergo changes related to the maturation of melanocytic nevi. In many cases it transforms into a compound nevus, in which melanocytes are located both in the epidermis and in the dermis, and then into an intradermal nevus.
From a dermatological point of view it is crucial to monitor lesions that meet the ABCDE criteria, which may suggest the development of melanoma:
- A – asymmetry,
- B – irregular borders,
- C – varied coloration,
- D – diameter greater than 6 mm,
- E – evolution of the lesion over time.
The appearance of such features is an indication for urgent dermatological consultation and further diagnostic work-up.
Junctional nevus – can it transform into melanoma?
A junctional nevus belongs to benign melanocytic nevi, however – similarly to other pigmented skin lesions – it requires periodic dermatological monitoring. Most nevi of this type do not undergo malignant transformation, but in dermatological diagnostics it is important to differentiate them from melanoma (melanoma malignum), i.e. a malignant tumor derived from melanocytes. Melanoma can develop both on the basis of a previously existing melanocytic nevus and in previously unaffected skin.
The risk of malignant transformation is relatively low for a single junctional nevus with typical clinical features. However, it increases in certain situations, such as:
- a large number of melanocytic nevi on the skin,
- the presence of atypical (dysplastic) nevi,
- fair skin phototype (I–II according to Fitzpatrick),
- frequent and intense exposure to UV radiation,
- a family history of cutaneous melanoma.
In clinical practice, assessment according to the ABCDE rule is of key importance, which helps detect early signs of melanoma:
| Criterion | Meaning |
|---|---|
| A – Asymmetry | asymmetrical shape of the lesion |
| B – Border | irregular, jagged borders |
| C – Colour | varied coloration (e.g. brown, black, red) |
| D – Diameter | diameter greater than 6 mm |
| E – Evolution | changes over time – enlargement, change in color or structure |
If such signs appear, an urgent dermatological consultation is necessary. The primary diagnostic tool is dermatoscopy, a non-invasive examination that enables assessment of the structure of a pigmented lesion at high magnification. Increasingly, digital video dermatoscopy is also used, which allows documentation of lesions and comparison of their appearance during subsequent follow-up visits.
If the dermatoscopic image raises diagnostic doubts, the recommended approach is surgical excision of the nevus with a margin of healthy skin and performing a histopathological examination. Only microscopic analysis of the tissue can definitively confirm the nature of the lesion and exclude the presence of malignant cells.
Regular monitoring of skin nevi, especially in people with numerous pigmented lesions or an increased risk of melanoma, is an important element of skin cancer prevention and early melanoma detection, which significantly improves prognosis and treatment effectiveness.
Junctional nevus – treatment
In most cases a junctional nevus does not require treatment if it has a typical clinical appearance and does not show features suggesting malignant transformation. The standard approach is periodic dermatological follow-up, often using digital dermatoscopy, which allows monitoring any changes in the nevus's structure over time.
Removal of the nevus may, however, be recommended in several situations:
- appearance of atypical features on dermatoscopic examination,
- rapid enlargement of the lesion,
- change in the color or shape of the nevus,
- chronic mechanical irritation (e.g., from clothing),
- cosmetic reasons.
The most reliable diagnostic and therapeutic method is surgical excision of the nevus with a margin of healthy tissue. The removed lesion is then subjected to histopathological examination, which allows definitive determination of its nature and exclusion of melanoma.
For benign lesions, procedural methods that improve the skin's appearance or remove pigmented changes are also used, such as:
- laser removal of skin lesions,
- laser therapy for pigmented lesions,
- dermatologic surgical procedures.
The choice of method depends on the lesion's location, its size, and dermatological assessment. In clinical practice, prior dermatoscopic diagnosis is always of key importance, because not every pigmented lesion should be removed by non-surgical methods.
Regular monitoring of skin nevi, especially in people with a large number of melanocytic nevi, a fair skin phototype, or a family history of skin cancers, is an important element of melanoma prevention.
