Fig. 2.
Bone marrow biopsy and aspirate in a patient with chronic eosinophilic leukemia carrying the FIP1L1-PDGFRA rearrangement. Increased numbers of hypogranulated neoplastic eosinophils are observed in the aspirate (A, B) (Wright-Giemsa, original magnification ×100). The infiltrate predominantly consists of eosinophils in a background of fibrosis in the biopsy (C, D) (Hematoxylin and Eosin, original magnification ×400) as opposed to mastocytosis whereby the predominant infiltrate is that of mast cells. (Courtesy of German A. Pihan, MD, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA.)