Auer rods in a patient with chronic myelomonocytic leukemia type 2.

A 69-year-old man presented with anemia (hemoglobin, 77 g/L), thrombocytopenia (platelets, 84 3 10 /L), and leukocytosis (white blood cell count, 31 3 10/L) including monocytosis (2.61 3 10/L). Blood film showed a leukoerythroblastic picture with nucleated red cells and blasts. Neutrophils had dysplastic features such as hyposegmented and hypersegmented nuclei, rare circular nuclei, and hypogranulation. Blasts, including myeloblasts, monoblasts, and promonocytes, comprised 8% of leukocytes. Some blasts contained Auer rods (panel A). Marrow aspiration demonstrated a hypercellular marrow with 13% blasts, including monoblasts and promonocytes which have open lacey chromatin and prominent nucleoli like monoblasts but with indented/ folded nuclei (Br J Haematol. 2014;165(3):273-286), trilineage dysplasia, and Auer rods (panel B). Flow immunophenotyping showed most blasts were CD34-negative, including myeloid and monocytic subsets. Cytochemistry was not performed. Cytogenetic analysis showed a normal karyotype. These findings were consistent with chronic myelomonocytic leukemia type 2 (CMML-2) as per the World Health Organization 2008 diagnostic criteria. Presence of Auer rods fulfilled criteria for CMML-2, irrespective of the blast count.