Case 72 - Discussion

Uploaded: 2007-11-72, Updated: 2007-11-30

Blue Nevus

• Blue nevi are most frequently noted in Asian populations, where the prevalence is estimated to be 3-5% in adults. They are found in 1-2% of white adults and are rarely found in blacks. Blue nevi are uncommon at birth or in the first few years of life.

• Two major variants

  • Common blue nevus:

    • Gross: a flat to slightly elevated, smooth surfaced macule, papule, or plaque that is gray-blue to bluish black. Usually solitary and found on the head and the neck, the sacral region, and the dorsal aspects of the hands and feet.

    • Histology: a vaguely nodular collection of poorly melanized spindled melanocytes and deeply pigmented dendritic melanocytes within thickened collagen bundles. Scattered melanophages are usually noted. No mitoses are present.

  • Cellular blue nevus:

    • Gross: a less common lesion but often clinically similar to the common blue nevus. Tend to be large, usually measuring 1-3 cm in diameter. Lesions are elevated, smooth-surfaced papules or plaques that are gray-blue to bluish black. Usually solitary and found on the buttocks, the sacral region, and occasionally on the dorsal aspects of the hands and the feet.

    • Histology: a well-demarcated nodule formed by fascicles and nests of tightly packed, moderately sized, spindled to oval melanocytes with scattered melanophages. The lesion is centered in the reticular dermis; blunt-ended, bulbous extensions that extend into the subcutaneous fat may be noted. Occasional mitoses may be present, but significant cytological atypia and areas of necrosis are absent. Often, a component of common blue nevus is seen within these lesions.

• Other variants of blue nevi: epithelioid blue nevus (classic description is with the Carney complex), atypical blue nevus, deep penetrating blue nevus, sclerosing blue nevus, and amelanotic blue nevus.

• Common blue nevi are clinically benign. The prognosis of blue nevi is excellent.

References

• http://www.emedicine.com/derm/topic55.htm