<prompt> In acute myeloid leukemia, Auer rods are numerous in:September 2009M2M3M4M5  <response>: Ans. B: M3The diagnosis of AML is based on the presence of at least 20 myeloid blasts in the bone marrow. Myeloblast have delicate nuclear chromatin, two to four nucleoli, and more voluminous cytoplasm than lymphoblasts.The cytoplasm often contains fine, peroxidase-positive azurophilic granules.Auer rods, distinctive needle like azurophilic granules, are present in many cases; they are paicularly numerous in AML with the t15;17 acute promyelocytic leukaemia-M3. 