Immunohistochemical staining for Ang2 protein in BM and LN biopsies. In BM, Ang2 immunoreactivity is mainly confined to infiltrating CLL cells (red), whereas other hematopoietic cells are mostly negative or slightly reactive (light pink; A-B). Notably, Ang2 expression is detected also in CLL cells displaying an intravascular distribution. No significant staining for Ang2 is observed on stromal and endothelial cells (A-B insets). Neoplastic cells diffusely effacing LN architecture display a clear positivity to Ang2, and such a reactivity does not involve endothelia (C). Original magnification, 200× for panels A and C, 400× for panel B.