What is AML?
Acute myeloid leukemia (AML) is an aggressive malignancy of immature, bone marrow-derived myeloid cells. It is the most common form of acute leukemia in adults and accounts for over 80,000 deaths worldwide each year. The World Health Organization (WHO) classifies AML into 22 subtypes which differ in prognosis and treatment. AML is associated with a wide variety of clinical presentations, morphological features, immunophenotypes, and genetic findings. Therefore, precise diagnosis and classification of AML require integration of morphology, immunophenotyping, cytogenetics, and molecular genetics. These methods are used together for classification, prognostic risk stratification, therapy selection, and disease monitoring.
AML Diagnostic Evaluation
The diagnostic workup of AML involves integration of patient history, clinical presentation, laboratory findings, and specialized pathological investigations. These studies include morphological evaluation of bone marrow aspirate, bone marrow biopsy, and peripheral blood smear, as well as immunophenotyping, cytogenetic tests, and molecular mutation analysis.
Fig. 1: Acute Myeloid Leukemia Diagnostic Evaluation
A diagnosis of AML requires either the presence of ≥20% myeloid blasts in the bone marrow or peripheral blood or the detection of specific cytogenetic abnormalities regardless of blast percentage. These abnormalities include balanced translocations, gene fusions, or certain molecular mutations.
Accordingly, in the 5th edition of the WHO classification, AML subtypes are grouped in the categories “AML with defining genetic abnormalities” or “AML defined by differentiation”. An exception is myeloid sarcoma which is a tumor mass that can occur at any anatomical site other than bone marrow and is composed of myeloid blasts.
Fig. 2: 2023 WHO Classification of AML Subtypes
AML Risk Groups
The European LeukemiaNet (ELN) 2022 guidelines classify AML into three prognostic risk groups based on genetic findings at initial diagnosis: favorable, intermediate, and adverse. Accurate prognostic assessment is central to the management of AML, as it guides treatment decisions, including the choice between standard- and higher-intensity therapeutic approaches.
Table 1: 2022 ELN Risk Classification and Detection Methods for Genetic Abnormalities
Why FISH is Important
FISH (Fluorescence in situ Hybridization) complements conventional karyotyping. It is particularly valuable when chromosomal abnormalities are cryptic, subtle, or when insufficient metaphases are available. FISH rapidly detects AML-defining rearrangements such as RUNX1::RUNX1T1, CBFB::MYH11, PML::RARA, KMT2A rearrangements and common abnormalities including -5/5q, -7/7q, and del(17p). These findings influence AML classification, prognosis, and treatment selection.
References
DiNardo CD, et al. 2023
Döhner H, et al. 2022
Narayanan D & Weinberg OK 2020
Pelcovits A & Niroula R 2013
Shimony S, et al. 2025
Short NJ, et al. 2018
Weinberg OK, et al. 2023
WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues, 5th Edition (2023)
Please select your region
Selecting your region and language ensures you receive the corresponding product portfolio and contact details.