FAB Classification of Acute Myeloid Leukemia (AML)

Overview

• FAB: Stands for French-American-British Classification.
• Based on Morphology: Looks at cell shapes and differentiation.
• Comparison: Previous WHO classification was based on cytogenetics, cell surface markers, clinical presentation.
• Subtypes: M0 to M7.

Subtypes of FAB Classification

M0

• Acute Myeloid Leukemia with Minimal Differentiation: AML-M0
• Cells have minimal similarity to normal progenitor cells.
• Morphology is barely differentiated.

M1

• AML without Maturation: AML-M1
• Presence of immature Myeloblasts without maturation into promyelocytes and mature cells.

M2

• AML with Maturation: AML-M2
• Maturation into Promyelocytes, which then mature further.
• Presence of mature cells alongside blasts.

M3

• Acute Promyelocytic Leukemia: AML-M3
• Promyelocytes' neoplastic proliferation.
• Myeloperoxidase (MPO) staining visible in cytoplasm.
• Translocation: Retinoic Acid Receptor translocation (15;17).
• Treatment: All-trans retinoic acid (ATRA) to convert immature cells to mature cells.

M4

• Acute Myelomonocytic Leukemia: AML-M4
• Neoplastic proliferation of both Myeloblasts and Monoblasts.

M5

• Acute Monoblastic Leukemia: AML-M5
• Neoplastic proliferation primarily of Monoblasts.

M6

• Acute Erythroid Leukemia: AML-M6
• Abnormal proliferation of erythroid precursors.

M7

• Acute Megakaryoblastic Leukemia: AML-M7
• Neoplastic proliferation of Megakaryoblasts.

Conclusion

The FAB classification system offers a morphologically-based approach to categorizing Acute Myeloid Leukemia (AML), ranging from M0 to M7. Each type provides distinct characteristics valuable for diagnosis and treatment strategies.