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.
Acute lymphoblastic leukemia
Acute megakaryocytic leukemia
Acute promyelocytic leukemia
Acute monocytic leukemia