Histological Findings. A: The perivascular epitheloid cells proliferate haphazardly around slit-like vascular channels, with aggregation of lymphoid cells. B: Tumour cells with expression of the HMB45-antigen. (immunohistochemistry with the avidin-biotin-peroxidase-complex method; counterstain haematoxylin; original magnification × 100). C: Focal coagulative necrosis of tumour cells (H&E; original magnification × 200).