Nevi of Special Sites


Displaced Junctional Nests in Breast Nevus
At 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 Nevus
These 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 Cytology
Higher 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 Atypia
Another 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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