BM sections from the patient in which the BCR/FGFR1 fusion gene originally was isolated show similarities with BCR/FGFR1-induced effects in the NOD/SCID and NSG mouse models. (A) Reticulin-stained section demonstrates a pronounced BM fibrosis and HE staining shows infiltration of blasts (top panel). Numerous macrophages staining positive for CD68 and occasionally mast cells, as defined by morphology and CD117 staining, are also found (middle panel). CD20⁺ B cells are more frequent than CD3⁺ T cells (bottom panel). Due to admixture of peripheral erythrocytes, a CD235 stained section could not be conclusively analyzed. (B) HE-stained section from a normal healthy BM.