PMC9948607_01
A 16x10mm atrophic erythematous plaque on her right chest.
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Physical examination showed a 16x10 mm asymptomatic, smooth, atrophic plaque ( Figure 1 ).
(A) Spindle cells infiltrate into the deep dermis and subcutaneous tissue, Hematoxylin-eosin (HE) x40; (B) Dense proliferation of spindle cells in a storiform pattern, HE x100; (C) Spindle cells are strongly positive for CD34, x40.
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Histopathologic examination revealed a monomorphic fibrohistiocytic spindle cell tumor arranged in a storiform pattern infiltrating the deep dermis and subcutaneous tissue forming honeycomb-like pattern ( Figures 2A, B ). Immunohistochemical analysis showed that cells were prominently positive for CD34 ( Figure 2C ) and negative for protein S-100.
PMC9948607_02
A round erythematous-to-bluish atrophic plaque.
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Physical examination showed a 30x20 mm round erythematous-to-bluish plaque with atrophy ( Figure 3 ).
Histopathological examination. (A) Fascicles of spindle cells with reduced dermal thickness by about half on low-power view, HE x40; (B) Monomorphic spindle cells with bland cytoplasm and scattered dendritic cells containing abundant melanin, HE x200; (C) Immunohistochemistry showed CD34+ cells infiltrating into subcutis and forming honeycomb-like pattern, x40; (D) Immunohistochemistry showed spindle cells were negative for S-100, in contrast, melanin-bearing dendritic cells were positive for S-100, x100.
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Cells containing brown pigment were scattered in the dermis ( Figures 4A, B ). Immunohistochemical staining showed that the spindle cells were diffusely positive for CD34 but negative for S-100 while melanin-laden dendritic cells were positive for S-100 ( Figures 4C, D ).