Figure 1: Skin biopsy from a patient with clinical features of GVHD. A: H&E section shows classic histopathological features of GVHD with interface dermatitis and apoptotic keratinocytes (arrows) (40x original magnification); B: C4d immunostain on the same patient in 1A shows focal positive staining in small dermal vessels (arrow) (40x original magnification).