Blue nevus in Child
Melanocytes originate embryologically in the neural crest and then migrate to the dermal-epidermal junction or to the hair bulb. Blue nevi are hypothesized to arise from melanocytes that fail to complete their developmental journey and instead reside and proliferate in the dermis. Dermal melanocytes reflect low-wavelength blue light but absorb higher wavelength light, a phenomenon known as the Tyndall effect. This accounts for the characteristic blue hue of the lesion. Somatic mutations in GNAQ mutations have recently been found in the majority of blue nevi.
A variant of blue nevus, the cellular blue nevus, is typically larger (1-3 cm in diameter) than a common blue nevus (<1 cm), solitary, and has a predilection for the buttocks or sacrococcygeal region. Malignant blue nevi are rare and tend to arise in cellular blue nevi, especially those on the scalp. Blue nevi are also one of the most common components of combined nevi. Another variant, the epithelioid blue nevus, may be associated with Carney complex (lentigines, atrial myxoma, mucocutaneous myxoma, and nevi).
Related topic: agminated nevus
D22.9 – Melanocytic nevi, unspecified
254806009 – Blue nevus of skin
Differential Diagnosis & Pitfalls
- Tattoos (eg, from a lead pencil or the mark used to locate radiation therapy fields) are flat and usually not as regular as a blue nevus.
- Nevus of Ota, nevus of Ito, and congenital dermal melanocytosis are blue but usually much larger and in characteristic locations.
- Melanocytic nevus
- Venous lake
- Angiokeratoma – often darker brown / black or with some red coloration
- Nodular melanoma – while rare in children, melanoma should always be considered and would be the main reason to biopsy