PMC5564110_01
(a) Numerous polygonal-oval red-brown plaques with well-demarcated borders in a symmetric distribution on the back. (b) Close-up view shows thickened epidermis with coarse wrinkling, mild scale, and underlying elongated region of erythematous to tan discoloration. (c) Dermoscopy reveals slight pink hue and prominence of network.
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Plaques ranged from 0.5 cm to 2 cm in size and were distributed haphazardly (Figures 1(a) and 1(b)). Dermoscopic exam was overall nondiagnostic and remarkable for a slight pink hue and prominence of network (Figure 1(c)).
(a) Hematoxylin and eosin, 10x. Superficial and deep perivascular small round blue cell infiltrate below a moderately hyperplastic epidermis with elongated rete ridges showing basal layer hyperpigmentation. (b) Hematoxylin and eosin, 40x. Perivascular infiltrates are comprised of plasma cells and fewer small lymphocytes.
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Histopathology revealed prominent superficial and deep perivascular and periadnexal infiltrate of hyperchromatic mononuclear cells (Figure 2(a)), with focal localization to small nerve twigs. Higher power examination revealed predominance of plasma cells lacking atypia in a background of small lymphocytes (Figure 2(b)).
(a) CD20 highlights a few aggregates of small B-lymphocytes. (b) CD138 shows the relative distribution of plasma cells around B-cell aggregates. (c) Kappa and (d) lambda immunohistochemistry shows a 3-4 : 1 ratio. (e) IgG is diffusely present in these plasma cells, while (f) IgM is mostly absent.
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Immunohistochemical stains highlighted the aggregates of CD20+, CD79A+, and B-lymphocytes (Figure 3(a)) amidst more numerous CD138+ (Figure 3(b)), IgD+, IgG+, and IgM- plasma cells (Figures 3(c) and 3(d)). Kappa and lambda in situ hybridization labeled the plasma cell population with a polytypic pattern including slight kappa predominance (normal finding) (Figures 3(e) and 3(f)).