## **Core Concept**
The diagnosis of Acute Myeloid Leukemia (AML) involves identifying blast cells in the bone marrow or peripheral blood. Blast cells are immature white blood cells that are not functioning properly. The World Health Organization (WHO) classification system is commonly used for the diagnosis of AML.

## **Why the Correct Answer is Right**
The correct answer involves the specific criteria used to diagnose blast cells in AML. According to the WHO classification, a diagnosis of AML is made when there are at least 20% blast cells in the bone marrow or peripheral blood. This is because the presence of 20% or more blast cells indicates a disruption in normal hematopoiesis, leading to the diagnosis of AML. The blast cells in AML are typically myeloblasts, which are primitive cells that would normally mature into granulocytes.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not specify the correct percentage or criteria for diagnosing blast cells in AML.
- **Option B:** This option is incorrect because it also does not provide the accurate threshold for the diagnosis of AML based on blast cell percentage.
- **Option D:** This option is incorrect as it likely presents an alternative criterion that does not align with the established threshold for diagnosing AML.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the diagnosis of AML requires the presence of at least 20% blast cells in the bone marrow or blood, according to the WHO criteria. This threshold differentiates AML from other myelodysplastic syndromes or acute lymphoblastic leukemia (ALL), which has a different treatment approach and prognosis.

## **Correct Answer:** . 20% or more blast cells.