Iliac crest bone marrow histology. Photomicrograph (CD79a immunohistochemistry) from 1 of the 2 PET⁻/BMB⁺ patients. The interstitial infiltrate by DLBCL was patchy, as in this field, but overall CD79a-positive cells amounted to ∼10% of all nucleated marrow cells (Nikon Eclipse 80i microscope and camera; ×40 objective).