Expression of the KSHV cyclin D gene in cutaneous KS lesions. (A) Early patch-stage lesion. Note hybridization signals in spindle cells forming the narrow vascular spaces in the dermis. (B) Nodular/tumor-stage lesion showing large numbers of hybridization signals in lesional spindle cells. (C) Well-formed blood vessel in the dermis adjacent to nodular lesion of KS. Note abundant hybridization signals in the vascular endothelial cells. (D) Plaque-stage lesion of KS with scattered keratinocytes in the overlying epidermis containing a few hybridization signals. Some of the labeled keratinocytes (arrows) are isolated and are surrounded by nonlabeled cells indicating that diffusion of label between cells did not occur. (E) Eccrine ductular epithelial cells containing hybridization signals. Only some of the eccrine epithelial cells are labeled in this plaque-stage KS lesion. Some of the labeled cells (arrows) are isolated and are surrounded by nonlabeled epithelial cells. (F) Nodular KS lesion containing scattered mononuclear cells, morphologically consistent with lymphocytes or histiocytes, which are labeled. All panels, ISH with catalyzed signal amplification, DAB chromogen, toluidine blue and hematoxylin counterstain. (A through F) Original magnification × 270.