Figure 2From: Progressive multifocal leukoencephalopathy in a patient without apparent immunosuppressionBiopsy specimen of the brain lesion. A, infiltrating foamy macrophages (arrows) and reactive astrocytes (block arrows) on hematoxylin and eosin stain of a deep white matter biopsy. B, positive stain for simian virus 40 (stains polyomavirus in humans).Back to article page