A melanocytic cuckoo - JAAD Case Reports

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Eccrine ducts opening onto the surface were also noted. ... more conventional compound nevus features superficially but dominated by blue nevuselike.
DERMOSCOPY

CASE OF THE MONTH

A melanocytic cuckoo Ciara Alice Maguire, MB, BCh, BAO,a Victoria Elliot, BSc FRCPath,b Birgit Pees, MD,a and Adam Rosen, BSc MBBSa

Southampton, England

CLINICAL PRESENTATION A 32-year-old man presented with a pigmented lesion on the left dorsal foot for as long as he could remember. Having observed a gradual change in peripheral color over many years, it had become more raised and occasionally itchy in the preceding year. There was no personal or family history of cutaneous malignancy. Clinical examination found a 10-mm 3 10-mm symmetrical square plaque with a peripheral tan-colored area surrounding central blue-black pigmentation (Fig 1).

Fig 1. Square pigmented plaque with symmetrical amorphous, darkly pigmented area centrally and surrounding pale brown rim.

DERMOSCOPIC APPEARANCE There was structureless, blue-black pigmentation centrally with adjacent peripheral light brown and patchy hypopigmentation. Multiple tiny circular white areas were evenly distributed throughout the central part, dissipating in the periphery. There was no apparent melanocytic network (Fig 2).

Fig 2. Dermoscopically, multiple tiny white dots resembling milialike cysts are diffusely distributed throughout the lesion in a ‘‘starry sky’’ pattern. From the Departments of Dermatologya and Cellular Pathology,b University Hospital Southampton NHS Foundation Trust. Funding sources: None. Conflicts of interest: None declared. Correspondence to: Adam Rosen, BSc MBBS, Department of Dermatology, Level E, Royal South Hants Hospital, Brintons Terrace, Southampton S014 0YG, England. E-mail: adam.rosen@ uhs.nhs.uk.

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JAAD Case Reports 2018;4:384-5. 2352-5126 Crown Copyright ª 2017 Published by Elsevier on behalf of the American Academy of Dermatology. All rights reserved. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/). https://doi.org/10.1016/j.jdcr.2017.10.013

JAAD CASE REPORTS

VOLUME 4, NUMBER 4

Maguire et al 385

HISTOLOGIC DIAGNOSIS Excision histology found a broadly symmetrical dermal melanocytic proliferation composed of plump melanocytes accompanied by dendritic pigmented cells. The melanocytes were arranged in short fascicles, sheets, and small nests and at the deep aspect broke up to interspect dermal reticular collagen fibers. There was no dysplasia on hematoxylin-eosin stain (H&E) or immunohistochemistry. Eccrine ducts opening onto the surface were also noted. The diagnosis was of a combined nevus with more conventional compound nevus features superficially but dominated by blue nevuselike attributes toward the base (Figs 3 and 4).

Fig 3. Medium-power magnification H&E stain preparation. Sections show a compound melanocytic proliferation with blue nevuselike features at the deep aspect (arrow).

Fig 4. High-power magnification H&E preparation. An eccrine sweat duct pore is seen within the lesion.

KEY MESSAGE The tiny white areas mimicking milialike cysts initially prompted a diagnosis of seborrheic keratosis but were not identified on histology. The pores of eccrine ducts may cause a perifollicular halo effect resulting in a similar presentation. Combined nevi may exhibit deceptive clinical appearances, but dermoscopic clues, such as areas of homogenous pigment, may suggest the diagnosis of a melanocytic lesion.