Blue Naevus

Synonyms: Tièche-Jadassohn naevus¹, Jadassohn-Tièche naevus¹, common blue naevus, cellular blue naevus, blue nevus (USA), chromatophoroma, melanofibroma.

This is a small blue or grey coloured lesion of the skin, with an appearance akin to a mole. They are present from a young age, but relatively unusual at birth (estimated prevalence ~1 in 1,000),² and do not change in size. They derive their blue colour from their pigmentation with melanin and relatively deep position within the epidermis, due to the optical properties of collagen in absorbing and scattering certain wavelengths of light (the Tyndall effect). One theory of their origin is that they represent embryonic neural crest cells that have failed to migrate into the epidermis in the usual fashion.² There are two forms:

• Common blue naevus:
  • Commonest form, 2–7mm or so in diameter
  • Slightly raised and smooth lesion with macular, papular or plaque-like appearance
  • Grey-blue to bluish-black in colour
  • Do not have any malignant potential
  • Usually a solitary lesion with a predilection for head (especially scalp), neck, sacral area and dorsum of the hands/feet.
• Cellular blue naevus:
  • Much rarer than the common form
  • Larger lesion, often 1–3 cm in diameter
  • Raised lesions with a smooth surface
  • Same colour as common form
  • Often solitary and found on buttocks, sacral region and back of hands/feet
  • May represent a subgroup of atypical melanoma, but this is uncertain, although the potential of the cellular form to undergo malignant transformation has been observed rarely.³

Commonest in Asian populations with a prevalence of 3–5% among adults. Prevalence in white populations is roughly 1–2%. Around twice as common in women compared to men.²

• Usually arise during the second decade and do not change in shape or size thereafter.
• They can rarely be present from birth.
• If the cellular form of the lesion undergoes malignant transformation this usually manifests as a precipitate increase in size or, more rarely, ulceration.²
• Can be found as pigmented lesions at unusual sites, e.g. female genitourinary tract,⁴ oral mucosa,⁵ beneath nails, spermatic cord, bronchus, lymph nodes and prostate.

• Malignant melanoma
• Dermatofibroma
• Melanocytic naevus
• Combined naevus
• Compound naevus
• Neurofibroma
• Histiocytoma
• Tattooing effect (deliberate, or material accidentally pushed into skin during trauma, e.g. coalminers' tattoo, ink pens)
• Thrombosed plantar wart
• Apocrine hydrocystoma
• Kaposi's sarcoma
• Congenital naevus
• Granuloma telangiectaticum
• Naevi of Ota and Ito.

• Carney's syndrome/complex is a rare association of blue naevi with further abnormalities of the skin and other organs, inherited in an autosomal dominant fashion.
• It causes cardiac, endocrine, cutaneous and neural myxomatous tumors, plus a variety of pigmented lesions of the skin and mucosae.⁷

None required as such. If the nature of a lesion is uncertain then dermoscopy may be performed by a dermatologist to distinguish it from melanomatous lesions.

• Typical lesions that have the appropriate history, that have not changed in size or shape and where there are no other features that would suggest an alternative diagnosis, or the presence of melanoma, can be left alone, and the patient reassured
• However, as for any pigmented lesion, where there is doubt as to the diagnosis it is safest to perform excision biopsy or refer for dermatological advice.
• Where the history is atypical, or the lesion has changed, refer for advice or perform excision biopsy
• There are occasional reports of recurrence of the lesion in a satellite form after excision; such lesions must be examined by further excision biopsy, preferably with dermatological opinion, to exclude malignant transformation.²

• Common blue naevi do not have any complications, are benign, and persist unchanged throughout life.
• Cellular blue naevi are also usually benign but may rarely undergo malignant transformation.
• Cellular naevi are larger and so more likely to present and undergo excision biopsy.

The prognosis for both types of lesion is excellent. In the rare cases where cellular naevi become malignant then prognosis is improved by earlier diagnosis, as for melanoma.