Blue naevus

Blue naevus
Other names	Blue nevus
File:Blue naevus.jpg
A typical blue naevus on the skin
Specialty	Dermatology
Symptoms	Blue or blue-black skin lesion
Complications	Rarely, malignant transformation
Usual onset	Usually present at birth or develops in early childhood
Duration	Lifelong
Causes	Proliferation of dermal melanocytes
Risk factors	None specific
Diagnostic method	Clinical examination, dermoscopy, biopsy
Treatment	Usually none required, surgical excision if necessary
Prognosis	Excellent
Frequency	Common

A blue naevus (or blue nevus) is a type of benign skin lesion characterized by its distinctive blue or blue-black color. This coloration is due to the presence of melanin-producing cells, known as melanocytes, located deep within the dermis.

Presentation

Blue naevi typically appear as solitary, well-circumscribed, dome-shaped papules or nodules. They are most commonly found on the dorsum of the hands and feet, but can occur anywhere on the body. The lesions are usually asymptomatic and are often discovered incidentally during a routine skin examination.

Pathophysiology

The blue color of the naevus is due to the Tyndall effect, where shorter wavelengths of light (blue) are scattered by the deep dermal melanocytes. This effect is similar to why the sky appears blue. The melanocytes in a blue naevus are spindle-shaped and are located in the mid to lower dermis.

Diagnosis

Diagnosis of a blue naevus is primarily clinical, based on its characteristic appearance. Dermoscopy can aid in the diagnosis by revealing a homogeneous blue pigmentation. In uncertain cases, a biopsy may be performed to rule out other conditions, such as malignant melanoma.

Differential Diagnosis

The differential diagnosis for a blue naevus includes:

• Malignant melanoma
• Mongolian spot
• Dermal melanocytosis
• Pigmented basal cell carcinoma

Management

Most blue naevi do not require treatment, as they are benign and have an excellent prognosis. However, if there is any change in size, shape, or color, or if the lesion becomes symptomatic, surgical excision may be considered to rule out malignancy.

Prognosis

The prognosis for a blue naevus is excellent, with a very low risk of malignant transformation. Regular monitoring is usually sufficient.

Also see

• Melanocytic nevus
• Dermoscopy
• Skin lesion
• Pigmentation disorder

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