Figure 1b. Lytic permeative pattern. (a) Photomicrograph (original magnification, x200; hematoxylin-eosin stain) of an intramedullary lesion of primary bone lymphoma reveals diffuse replacement of marrow elements by large atypical lymphocytes with large nuclei and a small amount of eosinophilic cytoplasm. (b, c) Photomicrographs (original magnification, x100; immunoperoxidase stain) show that the atypical cells stain strongly for common leukocyte antigen (b) but negatively for cytokeratin stain (c). Further testing showed that the cells stained positively for B-cell antigen. (For radiologic images, see Fig 2.)