A 42-year old female presents with the complaint of bleeding gums for the past 20 days. Intra-oral examination shows thickened and friable gums. Also, she has hepatosplenomegaly with generalized non tender lymphadenopathy. The blood count reveals: Hemoglobin 11.4 g/dl, Platelet count 90,000/mm3, WBC count 4600/mm3. The bone marrow biopsy shows 100% cellularity, with many large blasts that are peroxidase negative and nonspecific esterase positive. Which of the following is the most likely diagnosis for this patient?

Patient has an “aleukemic” leukemia in which leukemic blasts fill the marrow, but the peripheral blood count of leukocytes is not high. The staining of the blasts suggests the presence of monoblasts (peroxidase negative and nonspecific esterase positive). So, the likely diagnosis for her is M5 leukemia, which is characterized by increased chances of tissue infiltration and organomegaly. Other options: Acute lymphoblastic leukemia is typically seen in children and young adults. Acute megakaryocytic leukemia is typically accompanied by myelofibrosis and is rare. The blasts react with platelet-specific antibodies. Acute promyelocytic leukemia (M3-AML) has many promyelocytes filled with azurophilic granules, making them strongly peroxidase positive.