Relationship between Flt3-ITD status and distribution of phospho-STAT5 between nucleus and cytoplasm. The relative staining intensity for pSTAT5 was determined by manually scoring slides using a scale of 0 (neg) to 3 (+++) obtained from fixed bone marrow core biopsy of newly diagnosed patients with AML. Those scored as neg did not have detectable pSTAT5, and those scored as 3 had the highest intensity of staining. Shown are examples of patient samples with staining for nuclear pSTAT5 at each level. A patient sample showing predominant cytoplasmic pSTAT5 (++) is shown for comparison. Flt3-ITD status was determined by PCR on marrow clot sections using capillary electrophoresis. pSTAT5 Cy indicates cytoplasmic; pSTAT5 Nu, nuclear; and NA, not available. Slides were viewed with an Olympus BX50 microscope (Olympus, Center Valley, PA) using a 50×/0.90 oil-immersion objective lens and pSTAT5 immunostains. Images were acquired with an Insight 11.2 color mosaic camera (Diagnostic Instruments, Sterling Heights, MI) and processed with Spot Basic 4.1.3 (Diagnostic Instruments) and Adobe Photoshop elements 2.0 (Adobe, San Jose, CA) software.