What are the FAB classifications of acute myeloid leukemia?

Nov 03, 2025 Source: Cainiu Health

Dr. Liu Feng

Introduction

The FAB classification of acute myeloid leukemia generally includes M1 (acute myeloblastic leukemia without maturation), M2 (acute myeloblastic leukemia with maturation), M3 (acute promyelocytic leukemia), M4 (acute myelomonocytic leukemia), M5 (acute monocytic leukemia), and others.

　　The FAB classification of acute myeloid leukemia (AML) generally includes M1 (acute myeloblastic leukemia, minimally differentiated), M2 (acute myeloblastic leukemia with maturation), M3 (acute promyelocytic leukemia), M4 (acute myelomonocytic leukemia), and M5 (acute monocytic leukemia). A detailed analysis is as follows:

　　1. M1 (Acute Myeloblastic Leukemia, Minimally Differentiated): Characterized by a very high proportion of myeloblasts in the bone marrow with low differentiation. Patients commonly present with anemia, bleeding, and infections. Peripheral white blood cell counts are often elevated. Treatment primarily involves chemotherapy, and prognosis is influenced by the patient's age and overall health status.

　　2. M2 (Acute Myeloblastic Leukemia with Maturation): Features a high proportion of myeloblasts in the bone marrow along with some promyelocytes and more mature cells. Clinical manifestations are similar to those of M1; some patients may develop hepatosplenomegaly. Treatment strategies should be tailored based on cytogenetic characteristics.

　　3. M3 (Acute Promyelocytic Leukemia): Dominated by promyelocytes in the bone marrow, which contain numerous abnormal granules. Patients are prone to severe bleeding complications. However, this subtype shows excellent response to retinoic acid therapy, and with proper treatment, the prognosis is relatively favorable.

　　4. M4 (Acute Myelomonocytic Leukemia): Involves abnormal proliferation of both granulocytic and monocytic lineages in the bone marrow. In addition to common symptoms, patients may experience skin infiltration or gingival swelling. Treatment must target malignant clones from both cell lineages.

　　5. M5 (Acute Monocytic Leukemia): Characterized by predominant involvement of monoblasts and immature monocytes in the bone marrow. Patients are prone to extramedullary infiltration, such as gingival hyperplasia and skin nodules. Peripheral blood monocyte counts are significantly elevated. Intensive chemotherapy is required to control disease progression.

　　Accurate FAB classification relies on morphological examination of bone marrow cells. After diagnosis, individualized treatment plans should be developed incorporating immunophenotyping and genetic features. Regular follow-up bone marrow examinations and complete blood counts are essential for monitoring therapeutic response. Patients should take precautions against infection and bleeding and maintain balanced nutrition to tolerate treatment effectively.

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What is acute myeloid leukemia M5, and what should be done?

Acute myeloid leukemia M5 refers to acute monocytic leukemia. Under normal circumstances, acute monocytic leukemia may be related to factors such as unbalanced nutrition, excessive fatigue, chemical exposure, ionizing radiation, and viral infections. Patients are advised to adjust their diet, maintain a reasonable work-rest schedule, avoid exposure to ionizing radiation, and follow medical instructions for chemotherapy or treatment with ribavirin tablets.

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Can early-stage leukemia in children be cured?

In general, whether early-stage leukemia in children can be cured depends on the type of leukemia. Early-stage acute lymphoblastic leukemia is mostly curable, while some types of acute myeloid leukemia can be cured at the initial stage. Chronic myeloid leukemia is more difficult to cure completely in the early stage, but its progression can be controlled through treatment. In daily care, it is important to ensure balanced nutrition for the child, including adequate intake of protein and vitamins.

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Can acute myeloid leukemia M2A be cured?

In general, whether acute myeloid leukemia M2A can be cured depends on the severity of the disease. Patients with low- or intermediate-risk M2A have a good chance of cure with standardized treatment, while those with high-risk M2A are more difficult to cure, although active treatment can prolong survival. In daily care, it is important to provide patients with a clean and hygienic environment to prevent infections.

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Is acute myeloid leukemia M5 type severe?

In general, acute monocytic leukemia (M5) is one of the subtypes of acute myeloid leukemia with relatively high malignancy and carries a serious overall prognosis. However, outcomes vary among individuals and are influenced by factors such as patient age, chromosomal abnormalities, and timing of treatment. After diagnosis, individualized therapy should be initiated promptly in a hematology specialty setting. Younger patients who meet the criteria should actively pursue hematopoietic stem cell transplantation.