Acute myeloid leukemia (AML), also referred to as acute myelogenous leukemia, is a hematological malignancy characterized by the abnormal clonal proliferation of immature myeloid precursors (myeloblasts) or poorly differentiated cells of the hematopoietic system. It primary infiltrates the bone marrow, but the disease can also extend to blood and other tissues.
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Epidemiology
It is more common in middle-aged and elderly patients, with a median age of diagnosis at 70 years. The M:F rate varies from 1.1 in the 5th decade to about 1.8 in the 8th decade of life 2,3.
Acute myeloid leukemia only accounts for ~20% of all childhood leukaemias, cf. acute lymphoblastic leukemia (ALL), which represents ~80% of leukaemias at this age group 2.
There is an ethnic component in the distribution of most types of acute myeloid leukemia, with a strong predominance among the white ethnicity group 2,3.
Risk factors
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therapy-related acute myeloid leukemia (t-AML)
immunosuppression for a solid organ transplant
prior radiation therapy or chemotherapy
Clinical presentation
Acute myeloid leukemia tends to present with vague and non-specific symptoms such as fatigue and is most commonly revealed on full blood count tests, where anemia, thrombocytopenia, and/or neutropenia are demonstrated 2,4.
Described symptoms associated with bone marrow failure include 4:
bleeding gums
multiple ecchymoses
dyspnea on exertion
anginal chest pain
refractory upper respiratory infection symptoms
Extramedullary leukemic infiltration can lead to organ-involved signs such as hepatosplenomegaly, leukemia cutis, lymphadenopathy, gingival hyperplasia, and neurological symptoms 4.
Pathology
Location
The leukemic myeloblasts can commonly be identified either in peripheral blood smears or bone marrow aspirate. Eventually, there is infiltration of other organs and tissues:
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pulmonary complications tend to be observed more frequently at presentation in neutropenic AML patients of advanced age 7
Genetics
FMS‐like tyrosine kinase 3 (FLT3) mutation may play an important role in prognostication 9.
Classification
The 2022 World Health Organizatiοn (WHO) classification of haematolymphoid tumors classifies AML into multiple subtypes 5.
Depending on the type of cell lineage involved, AML can be divided into specific morphologic subgroups.
Microscopic appearance
The leukemic cells are characterized by very little cytoplasm, which holds fine azurophilic granules and Auer bodies or rods. Irregular nuclei and distinct nucleoli are also features of those cells 4.
Treatment and prognosis
Acute myeloid leukemia has an overall poor prognosis compared to the other main types of leukemia, having an approximately 30% 5-year survival rate 8. This is most evident among elderly patients over 65 years of age, where up to 70% succumbing to the disease within one year of diagnosis 8.