Fig. 4

A Microscopy revealed a well-encapsulated tumor with lymphoid cuffing; the tumor was composed of pigmented tumor cells and showed cystic degeneration (H&E stain, objective lenses ×4, original magnification ×40, scale bar 1000 μm). B Higher magnification revealed that the tumor cells had an epithelioid to spindle shape, mild nuclear atypia, small nucleoli, and abundant intracytoplasmic melanin pigments (H&E stain, objective lenses ×40, original magnification ×400, scale bar 100 μm). C Immunohistochemically, the tumor cells were positive for SOX10 (Objective lenses ×10, original magnification ×100, scale bar 100 μm). D Immunohistochemically, the tumor cells were positive for HMB45 (Objective lenses ×10, original magnification ×100, scale bar 100 μm). E Immunohistochemically, the tumor cells were positive for collagen type IV with a peri-tumoral circumferential pattern (Objective lenses ×10, original magnification ×100, scale bar 100 μm). F Immunohistochemically, the tumor cells were negative for AE1/AE3 (Objective lenses ×10, original magnification ×100, scale bar 100 μm). To acquire microscopic images, Nikon Eclipse Ni microscope, Nikon Plan Fluor series lenses, Nikon DS-Ri2 camera, and the acquisition software of NIS-Elements. 5.11.0 were used