Figure 1

a1–5, CMML. b1–5, chronic myelogenous leukemia (CML). c1–5, atypical chronic myeloid leukemia (aCML). a1—H&E of bone marrow section in CMML-1. Note the dwarf size megakaryocytes. b1—H&E section of CML. Small, unilobate megakaryocytes are typically seen in CML. c1—H&E section of aCML. Although there are subtle morphologic differences, the core biopsy findings of these three disorders (eg CMML, CML, and aCML) are quite similar. a2—CD68 (KP1) staining in CMML. Scattered myeloid cells and marrow macrophages are positively stained. b2—CD68 (KP1) staining in CML. Strong diffuse staining is seen in myeloid elements. c2—CD68 (KP1) staining in aCML. Diffuse staining is also seen. a3—CD68R (PGM-1) staining in CMML. CD68R-positive bone marrow macrophages are seen. Inset: note the few positive monocytes also stained. b3—CML and c3—aCML, CD68 (PGM-1) staining. Only marrow macrophages stain positively. a4—CMML, b4—CML, c4—aCML, CD163 stained mostly bone marrow macrophages in all three groups. a5—CMML, no increase in blasts are identified by CD34 staining in this case of CMML. b5—CML and c5—aCML, rare blasts stain for CD34. Note the increased vascular density highlighted by CD34.