Naevi intradermiques et composés

See also the separate Pigmented skin lesions article.

What are intradermal naevi?^{1 2}

Intradermal naevi are a form of melanocytic naevus. A melanocytic naevus (or 'mole') is a common benign skin lesion due to a local proliferation of pigment cells (melanocytes). A brown or black melanocytic naevus contains the pigment melanin, so may also be called a pigmented naevus.

An intradermal naevus has naevus cell nests in the dermis, and presents as a papule, plaque or nodule with a pedunculated, papillomatous or smooth surface.

Some intradermal naevi may have the same degree of pigmentation as the surrounding skin. They are the classical skin or flesh-coloured 'mole', elevated from the skin's surface, that most people would recognise as such. Some are pigmented.³

Intradermal naevi may appear spontaneously or grow from a pre-existing pigmented mole. They usually develop from the end of childhood onwards and may appear at any stage throughout adulthood, although they are probably quite rare as a new phenomenon after the age of 60. Intradermal naevi have the following characteristics:

• Small (5 mm-1 cm).

• Raised from the surface of the skin (rounded, dome-shaped, pedunculated or warty appearance).

• May be associated with hair growth (particularly in older patients).

How common are intradermal naevi? (Epidemiology)⁴

Intradermal naevi are extremely common, as are all the melanocytic naevi. Indeed they affect so many people that some consider that they cannot be classed as a pathological entity - rather, a normal variant.

Symptoms of intradermal naevi

• Intradermal naevi do not present that often, as most people recognise them as a benign dermatological phenomenon.

• They may be detected coincidentally during a consultation, or brought up as a 'whilst I'm here' phenomenon.

• They are most likely to present if they are newly noticed.

Visual appearance of intradermal naevi

Intradermal naevi

By Unknown photographer, Public domain, via Wikimedia Commons

Diagnostic différentiel⁵

• History and appearance of intradermal naevi are fairly characteristic and so they are not usually confused with other lesions.

• They may resemble early basal cell carcinoma or a neurofibroma.

• Basal cell carcinoma will usually have a shorter history, be noted to be growing quite quickly and have associated telangiectasia.

• Where there is doubt as to the diagnosis then excision biopsy will resolve the question.

Enquêtes

• None is usually required.

• If there has been significant recent growth of intradermal naevi then consider excision biopsy to exclude basal cell carcinoma.

• Where a previously non-pigmented lesion develops pigmentation then excision biopsy should be carried out.

Intradermal naevi treatment

• No treatment is required unless the patient is concerned about the lesion's cosmetic appearance or there are suspicions of an alternative diagnosis.

• Excision biopsy may be used for diagnostic purposes.

• Shave and cautery (dermal electrosurgical shave excision) are a good method for removing them, with apparently better cosmetic results than excision biopsy.⁶

• Injection of local anaesthetic directly into the lesion before shaving may improve the cosmetic result.⁷

• Facial lesions may be best removed for cosmetic purposes by a dermatological surgeon or plastic surgeon, particularly in young patients, due to the high risk of medicolegal claims in this area of practice if there is a poor cosmetic outcome.

Complications et pronostic

• Intradermal naevi have no complications as such and are benign, slow-growing lesions.

• If they occur in the external auditory meatus they can obstruct the auditory canal and impair hearing.⁸

• There are potential complications associated with their removal.

Prognosis is excellent, as it is a benign lesion with no risk of transformation to melanoma.

What are compound naevi?²

Compound naevi have nests of naevus cells at the epidermal-dermal junction as well as within the dermis, and present as a central raised area surrounded by a flat patch.¹

Compound naevi are dark brown in colour. Compound naevi are considered to be benign neoplasms of melanocytes if they arise in later life.⁹

Compound naevi arise from a flat (junctional) naevus that exists earlier in life and may have a raised central portion of deeper pigmentation with surrounding tan-brown macular pigmentation. Pigmentation may be uneven within the naevus but is usually symmetrically distributed. Compound naevi are usually of a round/oval shape and roughly 2 mm-7 mm in diameter. They may exist with a variable degree of pigmentation and even be the same colour as the surrounding skin. Their name is derived from the fact that they contain junctional melanocytes (responsible for their pigmentation) and intradermal melanocytes (responsible for the elevation of the lesion).

How common are compound naevi? (Epidemiology)

Melanocytic naevi in the general population are exceedingly common in congenital and acquired form. Their prevalence is so high that some believe they cannot even be considered an abnormality or pathological entity, as most people with light-coloured skin will have at least a few.¹⁰

Compound naevi are much more common in ethnic groups with light skin but they still have an appreciable prevalence in those with more pigmented skin. Congenital melanocytic naevi occur in approximately 1% of newborns at birth. Acquired melanocytic naevi are usually seen from the age of one year, peak in number during the second and third decades of life and disappear between the seventh to ninth decades.¹¹

Signs and symptoms of compound naevi (presentation)

Compound naevi symptoms

• Establish if the lesion is congenital or acquired (compound naevi are acquired).

• Lorsqu'une lésion se présente médicalement, il est important de vérifier s'il y a eu des symptômes associés tels que

  • Élargissement.

  • Changement de forme ou de taille.

  • Changement de pigmentation.

  • Démangeaisons/douleurs/irritations.

  • Saignement.

Compound naevi signs

• Examinez la lésion à la lumière vive, de préférence à la lumière du jour si vous en disposez.

• Use drawings or photography to note the site(s), size or shape and pigmentation of the lesion.

• Establish that the lesion has the typical pattern of pigmentation and is raised from the level of the skin.

• Distinguish from other similar raised benign tumours of the skin:

  • Dermatofibromas tend to feel firm or hard on palpation, whereas compound naevi are softer.

  • Seborrhoeic warts tend to have a 'stuck-on' appearance, rather than blending into the surrounding skin.

  • Le mélanome a tendance à être plus foncé, à avoir un bord irrégulier, à être asymétrique et à s'être développé récemment.

Visual appearance of compound naevi

Compound naevus with size gauge

Par Jmarchn, CC BY-SA 3.0via Wikimedia Commons

Compound naevus on left buttock

By Dermanonymous, CC BY-SA 4.0, via Wikimedia Commons

Diagnostic différentiel⁵

• Mélanome malin.

• Lentigines.

• Môle atypique (naevus dysplasique).

• Autres naevi mélanocytaires.

• Pyogenic granuloma (usually reddish but may be brown).

• Seborrhoeic keratosis.

• Acanthome.

• Histiocytome.

• Skin tag (acrochordon).

• Kératose actinique.

• Neuroma.

• Carcinome épidermoïde.

• Naevi d'Ota et d'Ito.

Diagnosing compound naevi (investigations)

• No investigations are indicated in the case of a common, acquired compound naevus that has not undergone any recent change.

• Some dermatologists may use dermoscopy to try to distinguish the nature of pigmented lesions.¹²

• If there is any suspicion of malignant melanoma then the investigation of choice is excision biopsy.

Compound naevi treatment

• If the diagnosis of compound naevus is clear and there has been no change in a long-standing lesion then reassurance and monitoring of the lesion are all that is usually required.

• Where there is any doubt as to the diagnosis of compound naevi, perform excision biopsy or refer for dermatological advice.

• Effectuer une biopsie d'excision chaque fois que la lésion a.. :

  • Cultivé.

  • Devenir symptomatique.

  • Asymétrie développée.

  • A développé une bordure irrégulière.

  • Modification de son degré ou de son modèle de pigmentation.

  • Lésions satellites développées.

Complications et pronostic

Compound naevi are benign lesions. They do not cause complications and they have an excellent prognosis.