A 42 -year old man was referred with a 2 week history of fever weakness and bleeding gum. Peripherial smear showed pancytopenia. The bone marrow examination revelaed 26% blasts frequently exhibiting Auer rods and mature myeloid cells. An occasional neutrophil with pseudo Pelger-Huet anomaly was also noted : Which of the following cytochemical stains is most likely to be positive -

The symptoms and laboratory finding of the patient confirms the diagnosis of AML. Let us discuss each findings - H/o fever weakness and bleeding gum - Most of the books agree that patients of acute leukemia present with nonspecific symptoms as fatigue, fever, weight loss. These are consequence of anemia or leucocytosis. Some patients may also present with signs of abnormal hemostatis such as bleeding gum. Peripheral smear shows pancytopenia- The no. of Leukemic cells in peripheral blood in AML is highly variable sometimes being more than 10000 cell/ ml but being under 10,000 in 50% of patients. Occasionally the peripheral smear may not contain any blasts (aleukemic leukemia). So even in pts with ancytopenia bone marrow examination is essential to exclude acute leukemia. Bone marrow examination reveals 26% blast/cells :- Harrison says - "The diagnosis of AML is' established by presence of more than 20% myeloblast in bone marrow." The blast cells were mature and contain Auer rods: Auer rods are red staining rod like structures (representing abnormal azurophilic granules) present in myeloblast in AML. The presence of Auer rods is considered as definite evidence of myeloid differentiation. They are most numerous in M3 form of AML. Neutrophil with Pseudo Pelger Huet anomaly :-  Pseudo Pelger Huet cells are neutrophils with only 2 nuclear lobes and are frequently seen in myelodysplastic syndrome. Myelodysplatic syndrome progresses to AML in10% of cases so it can be assumed that in this patient AML has developed from myelodysplastic syndrome.