What are the steps to diagnose Acute Myeloid Leukemia (AML)?

Diagnostic Steps for Acute Myeloid Leukemia (AML)

The diagnosis of AML requires a comprehensive evaluation of peripheral blood samples and bone marrow aspirates, including morphological examination, cytochemistry, immunophenotyping, and cytogenetic analysis. 1

Initial Diagnostic Workup

Clinical Assessment

• Obtain comprehensive medical history including any history of possibly confounding factors such as recent growth factor therapy, transfusions, or medications that might obscure or mimic features of acute leukemia 1
• Document family history of hematologic disorders or other malignancies 1
• Provide relevant physical examination findings including neurologic examination and presence of tumor masses, cutaneous lesions, or organomegaly 1

Laboratory Evaluation

• Review complete blood count (CBC) with platelets and white blood cell differential 1
• Evaluate peripheral blood smear for morphologic assessment 1
• Obtain comprehensive metabolic panel 1
• Assess serum uric acid and lactate dehydrogenase levels which have prognostic relevance 1
• Perform coagulation screening prior to invasive procedures 1

Bone Marrow Examination

Collection and Processing

• Obtain fresh bone marrow aspirate for all patients suspected of AML 1
• Prepare bone marrow aspirate smears for morphologic evaluation 1
• Evaluate bone marrow trephine core biopsy, trephine touch preparations, and/or marrow clots in conjunction with aspirates 1, 2
• If bone marrow aspirate is inadequate, peripheral blood may be used if sufficient blasts are present 1
• If aspirate is unobtainable, prepare touch imprint preparations from core biopsy and submit additional core biopsy in tissue culture medium for disaggregation 1

Essential Diagnostic Studies

• Perform conventional cytogenetic analysis (karyotype) 1
• Conduct flow cytometry immunophenotyping with a panel sufficient to distinguish AML, including early T-ALL, B-ALL, and AL of ambiguous lineage 1
• Perform appropriate molecular genetic and/or FISH testing 1
• Consider cytochemical studies to assist in diagnosis and classification 1

Molecular and Genetic Testing

Required Molecular Testing

• Test for FLT3-ITD in all patients with suspected or confirmed AML 1
• For CBF AML (with t(8;21) or inv(16)/t(16;16)), ensure KIT mutation analysis 1
• For suspected APL, perform rapid detection of PML-RARA 1
• For non-CBF AML, non-APL cases, perform mutational analysis for NPM1, CEBPA, and RUNX1 1

Additional Molecular Testing

• Consider mutational analysis for IDH1, IDH2, TET2, WT1, DNMT3A, and/or TP53 for prognostic and therapeutic purposes 1
• Ensure testing is comprehensive enough to allow subsequent detection of measurable residual disease (MRD) 1
• Store samples appropriately for potential future molecular or genetic studies 3

Special Considerations

Extramedullary Disease

• If extramedullary disease is suspected, perform PET/CT 1
• For patients with significant CNS signs or symptoms, evaluate using appropriate imaging (radiography, CT, or MRI) 1
• For extramedullary disease without bone marrow or blood involvement, evaluate tissue biopsy specimen with the same workup as recommended for bone marrow 1

Cerebrospinal Fluid Evaluation

• For patients with ALL receiving intrathecal therapy, obtain CSF sample with cell count and examination of cytocentrifuge preparation 1
• Consider CSF evaluation in other AML patients when clinically indicated 1
• Flow cytometry may be used in the evaluation of CSF 1

Risk Assessment and Classification

Risk Stratification Factors

• Age of the patient (>60 years associated with adverse prognosis) 1
• Initial leukocyte count 1
• AML subtype according to WHO/ICC classification 4
• Cytogenetic abnormalities (favorable: t(15;17), t(8;21), inv(16)) 1
• Molecular mutations (NPM1, FLT3-ITD, CEBPA, etc.) 1
• History of antecedent myelodysplastic syndrome or therapy-related AML 1, 5

Quality Control

• Ensure all laboratory testing is performed in laboratories compliant with regulatory requirements 1
• Ideally, the same physician should interpret both bone marrow aspirate smears and core biopsy specimens 1

Pitfalls to Avoid

• Do not postpone collection of diagnostic samples for molecular and genetic studies 6
• Avoid starting chemotherapy before obtaining satisfactory material for all diagnostic tests 1
• Do not rely solely on peripheral blood for diagnosis when bone marrow examination is feasible 2
• Remember that conventional cytogenetic analysis cannot be replaced by molecular genetic or FISH testing alone 1
• Be aware that certain mutations are associated with germline predisposition, which may warrant family screening 6