What is the required blast count percentage for diagnosing AML according to the WHO classification?

In the context of diagnosing Acute Myeloid Leukemia (AML), the World Health Organization (WHO) classification specifies that at least 20% of the cells in the bone marrow or blood must be blasts for a definitive diagnosis. This threshold is important because it helps distinguish AML from other hematological conditions, such as myelodysplastic syndromes, where the percentage of blasts is typically lower. The presence of a high percentage of these immature cells indicates that the bone marrow is not functioning properly and is characterized by the proliferation of abnormal cells, which is central to the pathology of AML. The requirement for this specific percentage ensures that the diagnosis is accurate and that appropriate treatment can be initiated.