Nevi of Special Sites

Displaced Junctional Nests in Breast NevusAt this low power, a junctional melanocytic proliferation is evident on the breast of a 25-year-old woman. Most nests image appear at the tips of rete ridges. However, there are apparently displaced nests on the left side of the lesion image.

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Papillary Dermal Fibroplasia in Breast NevusThese nests image appear to be overlying papillary dermal fibroplasia image and are not laterally displaced or fused as seen in atypical/dysplastic nevi.
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High Magnification: Banal CytologyHigher power examination exhibits no macronucleoli, vesicular nuclei, or hyperchromasia. Note how the nests image blend in with epidermal keratinocytes.
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High Magnification: Lack of Cytological AtypiaAnother focus of the same lesion shows nested melanocytes devoid of cytological atypia. Note the melanin incontinence image and sparse lymphohistiocytic inflammation image in the superficial dermis.

TERMINOLOGY

Synonyms

• Melanocytic nevi of special sites

Definitions

• Benign melanocytic nevi with unusual histological features that can mimic dysplastic nevi or melanoma
image Unusual histopathologic findings are attributed to anatomic location and not neoplastic features
image Architectural &/or cytological abnormalities do not correlate with aggressive clinical behavior

CLINICAL ISSUES

Presentation

• Special site designation includes the following anatomic locations
image Acral
image Genital
image Scalp
image In and around ear
image Breast and milk line
image Flexural skin (skin folds at axillae, antecubital and popliteal fossae, and umbilicus)

Treatment

• Surgical approaches
image Shave or simple excision

Prognosis

• Excellent

MACROSCOPIC

General Features

• Light to dark brown papule or plaque with areas of pigmentary change
• Dermoscopy can show prominent pigment network, sometimes with bizarre lines, and large globules

MICROSCOPIC

Histologic Features

• Asymmetry and poor peripheral circumscription
• Large junctional nests of melanocytes located at tips, sides, and between rete ridges
image Some nests are randomly scattered along dermoepidermal junction, resembling atypical/dysplastic nevi
image Nests show variation in shape with frequent bizarre forms
image Dyscohesion of tumor cells within nests
• Involvement of skin adnexa
• Focal poorly nested, lentiginous proliferation of melanocytes along dermoepidermal junction
• Focal upward migration of isolated melanocytes in central part of lesion, especially if traumatized
• Dermal melanocytic component is cytologically bland
image Matures properly with increasing dermal depth
image Occasional mitotic activity can be seen
image Cell are set in fibroplasia or may be focally inflamed

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Apr 24, 2017 | Posted by in PATHOLOGY & LABORATORY MEDICINE | Comments Off on Nevi of Special Sites

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