Histology of hypereosinophilic syndrome in AML. (A) Marked eosinophilia in the bone marrow at the last relapse (original magnification ×40; inset ×400; hematoxylin and eosin stain). Eosinophilic infiltrate in (B) lymph node, (C) adrenal medulla (inset: CD34 immunostain), and (D) liver at autopsy. Original magnification by ×400, hematoxylin and eosin stain, except as noted.