Figure 2

Endocardial biopsy demonstrating active myocarditis without fibrosis in a pediatric allogeneic hematopoietic stem cell transplant patient with fulminant myocarditis. (a) At low magnification, the myocardium is diffusely inflamed (hematoxylin and eosin, calibration bar=150 μ). (b) High magnification discloses a predominantly mononuclear cell infiltrate with scattered eosinophils (arrowheads; hematoxylin and eosin, calibration bar=20 μ). Gaps between myofibers signify myocyte damage. (c) By immunoperoxidase methods, Ab to CD8 highlights numerous cytotoxic T-lymphocytes with brown reaction product (immunoperoxidase with 3,3′-diaminobenzidine, calibration bar=20 μ).