Blue Nevi Workup

Updated: Sep 18, 2020
  • Author: Rudolf R Roth, MD; Chief Editor: William D James, MD  more...
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Workup

Laboratory Studies

Laboratory studies are not necessary.

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Imaging Studies

Imaging studies generally are not necessary; however, dermoscopy is a useful method for separating common blue nevi from a melanoma. The classic dermatoscopic features include a homogeneous steel-blue color with no pigment network, no aggregated globules, and no branched streaks, [19, 20, 21] although variations, including blue globules and dots and pigmented networks, have been reported. [22]

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Histologic Findings

A histologic continuum exists from common blue nevi to cellular blue nevi.

In common blue nevus, a vaguely nodular collection of poorly melanized spindled melanocytes and deeply pigmented dendritic melanocytes within thickened collagen bundles is seen. Scattered melanophages are usually noted. No mitoses are present.

Common blue nevus. Numerous elongated dendritic me Common blue nevus. Numerous elongated dendritic melanocytes with a subepidermal grenz zone. Courtesy of Rose Elenitsas, MD.

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

Cellular blue nevus. Deep proliferation of dendrit Cellular blue nevus. Deep proliferation of dendritic melanocytes, broader at the surface than the base, with islands of paler cells with larger nuclei. Courtesy of Rose Elenitsas, MD.

A number of variants of blue nevi with corresponding histologic changes have been described, including epithelioid blue nevus (classic description is with the Carney complex, but also is seen without this condition), atypical blue nevus, deep penetrating blue nevus, sclerosing blue nevus, and amelanotic blue nevus. [23, 24]

The term malignant blue nevus is synonymous with malignant melanoma arising in association with a cellular blue nevus or growing in a histologic pattern similar to that of a cellular blue nevus. These lesions typically have a pronounced cytologic atypia, hyperchromasia, necrosis, an increased mitotic rate, and an infiltrative growth pattern. [25] Complete excision with a margin of healthy skin according to National Comprehensive Cancer Network (NCCN) guidelines should be performed.

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