INTRODUCTION The blue nevus was first described by Tieche in 1906. It gets its name from its blue color that results from the concentration of melanin in its location in the deep dermis and the Tyndall effect of differential absorption of long wavelengths of light. It is believed to represent dermal arrest in embryonal migration of neural crest melanocytes that fail to reach the epidermis. The blue nevus is composed of pigmented dermal melanocytes and is represented by two histolog-ic types: the common blue nevus and the cellular blue nevus. These two variants can sometimes be differentiated on clinical appearance. LAMB syndrome is the association of blue nevi with lentigines and skin papules and underlying atrial cardiac myxomas.
CLINICAL PRESENTATION The common blue nevus appears as a solitary, smooth surfaced, well-circumscribed oval lesion that is flat to slightly elevated. It is usually less than 1 cm in diameter. Blue nevi vary in color from blue to blue-black and may have a grey or whitish center. They occur most often on the back of the hands, face, and on the buttocks. While they usually occur in the skin, blue nevi can also be seen in the sclera, conjunctiva, and orbit. When present from birth the nevus typically remains unchanged throughout life, but most develop later in life and can show very slow growth.
HISTOPATHOLOGY The common blue nevus is characterized by elongated melanocytes present between collagen bundles of the mid and upper dermis. Melanophages contain much of the pigment present in these lesions.
DIFFERENTIAL DIAGNOSIS The differential diagnosis includes cellular blue nevus, dermatofibroma, oculodermal melanocytosis, malignant melanoma, pigmented basal cell carcinoma, Kaposi's sarcoma, and vascular lesions.
TREATMENT Treatment is not necessary as long as the diagnosis is assured. If there is any change in pigmentation a biopsy should be performed. When removal is desired for diagnosis or cosmesis, simple surgical excision is recommended. It is important to include deep subcutaneous tissue because these nevi often extend into the subcutis.
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