#00061455

An 81 year old man presented with fatigue, abdominal pain, and epistaxis. An automated complete blood count performed on a Sysmex XN-9100 instrument showed the following values: White blood cells (WBC), 26.7K/mcL (61.7% neutrophils, 13.1% lymphocytes, 11.6% monocytes, 0.4% eosinophils, 0.4% basophils, 12.8% immature granulocytes); red blood cells, 3.34M/mcL; hemoglobin, 10.2g/dL; MCV 88.1fL, RDW 13.9%; platelets 57K/mcL; and nucleated RBCs, 0.7 per 100 WBCs. The results were flagged for “immature granulocytes present” and “blasts/abnormal lymphocytes?” by the analytical software. Automated microscopic examination of the WBCs using a CellaVision DM96 (Sysmex) provided the images shown in panel A, which depict left-shifted neutrophils and monocytosis (second row from bottom) but no blasts. In contrast, the XN-9100 WBC differential scatterplot showed a prominent cell population with intense side fluorescence (SFL) (dotted circle, panel B).  The discordance is explained by a high concentration of very large blasts at the feathered (C) and lateral (D) edges of the smear, which are not photographed by CellaVision. Acute myeloid leukemia was diagnosed on marrow examination. This case illustrates the importance of examining the edges of the blood film for large cells that are pushed there by spreader during smear preparation.