Fig. 4
Comparison of histologic and PIK3CG immunohistochemical features of the primary skin and three metastatic lesions in the brain. All melanomas from the skin primary (a), 1st. (c), 2nd (e) and 3rd. (g) metastases in the brain were histologically similar with highly-atypical epithelioid malignant cells with prominent nucleoli, conspicuous cytoplasm, focal finely-granular green-yellow pigment, high mitotic activity (arrows), and necrosis (*). PIK3CG was negative in the skin primary (b; inset: negative control; *: epidermis), and focally and weakly positive in all three brain metastases (d; inset: positive control, f and h), with the 3rd metastatic lesion in the brain having a more widespread and stronger positivity (h), relative to others. (Original magnifications: a–h: 400 ×; insets: 200 ×)