Fig. 4

Pathological findings of a brain biopsy from the left frontal lesion. A, B In low-magnification view of hematoxylin–eosin (HE) and Klüver-Barrera (KB)-stained sections. The sampled lesion consisted of inflammatory cell infiltration and myelin loss. C, D High-magnification view of HE. HE staining showed foamy macrophage infiltration and atypical astrocytes. E KB staining demonstrated demyelination with myelin-laden macrophages. F Double-staining of KB and neurofilament immunostaining revealed relatively preserved axonal structures compared to myelin. G Immunostaining showed that the infiltrating cells were CD68 ⁺ . H Immunohistochemistry using an anti-JCV VP2/3 antibody indicated the presence of JC virus antigen-positive cells. Scale bars: 200 μm (A, B), 20 μm (C–F, H), and 50 μm (G)