case_images: PMC11806390_01
case_images: Left forearm excisional biopsy findings. A: Hematoxylin and eosin staining showing the proliferation of spindle-shaped, non-pigmented nevomelanocytes in the papillary dermis (arrows). B. Immunohistochemical examination of S100 revealing positive staining in all tumor cells (arrows); pigment granules from black tattoo ink in the macrophages of the stroma between proliferating nevomelanocytes (asterisks). C. Immunohistochemical examination of Melan-A showing positive staining in all tumor cells (arrows) and black ink pigment granules in stromal macrophages (asterisks). D. Immunohistochemical examination of SOX-10 revealing positive expression in all nevomelanocytes (arrows) and pigment granules from black ink in stromal macrophages (asterisks). E. Immunohistochemical examination of HMB-45 showing negative expression in nevomelanocytes, with positive expression in basal melanocytes serving as an internal control (arrows). F. Immunohistochemical examination of BRAF showing positive expression in all nevomelanocytes (arrows). Staining with red pigment (EnVision FLEX HRP Magenta Substrate, Dako Omnis, Agilent Technologies, Santa Clara, CA). Magnification: x100
case_images: cureus-0017-00000077180-i01.jpg
case_images: PMC11806390_01_cureus-0017-00000077180-i01.jpg
case_images: FIG1
case_images: Routine histopathological examination showed a dermal, circumscriptive proliferation of spindle-shaped, non-pigmented nevomelanocytes with well-defined eosinophilic cytoplasm, oval vacuolated nuclei, and small, uniform nucleoli (Figure 1A). Additionally, there was deposition of black pigment from the tattoo ink outside the tumor cells and within stromal macrophages (Figures 1B-1D). Immunohistochemical analysis revealed that all the proliferated nevomelanocytes stained positively for S100 (Figure 1B), Melan-A (Figure 1C), SOX-10 (Figure 1D), and BRAF (Figure 1F), while remaining negative for HMB-45 (Figure 1E).