What diagnostic steps and treatment options should the provider consider for a suspected case of acute leukemia?

Comprehensive Diagnostic Workup for Suspected Acute Leukemia

Patients should advocate for their provider to obtain sufficient bone marrow and blood samples with comprehensive ancillary testing including conventional karyotyping, flow cytometry immunophenotyping, and molecular genetic analysis—all performed simultaneously at initial diagnosis to enable accurate classification, risk stratification, and treatment planning. 1

Essential Initial Specimen Collection

The provider must obtain:

• Bone marrow aspirate smears, trephine core biopsy, and marrow clots for morphologic assessment 1
• Peripheral blood samples if sufficient circulating blasts are present (can substitute for bone marrow in some cases) 2
• Adequate sample volume to perform all required ancillary studies without needing repeat procedures 1

Critical pitfall: If bone marrow aspirate is inadequate ("dry tap"), the provider should prepare touch imprint preparations from the core biopsy and submit an additional unfixed core biopsy in tissue culture medium for disaggregation for flow cytometry and genetic studies 1. This prevents diagnostic delays.

Mandatory Ancillary Testing (Must Be Performed Simultaneously)

Flow Cytometry Immunophenotyping

The panel must be comprehensive enough to distinguish:

• Acute myeloid leukemia (AML) including acute promyelocytic leukemia (APL)
• B-cell acute lymphoblastic leukemia (B-ALL)
• T-cell acute lymphoblastic leukemia (T-ALL)
• Acute leukemia of ambiguous lineage 1, 3

The flow cytometry analysis must also be designed to enable future measurable residual disease (MRD) detection 1, 4

Conventional Cytogenetic Analysis (Karyotype)

This is mandatory and cannot be replaced by FISH or molecular testing alone 1. The karyotype identifies:

• Favorable risk: t(15;17) for APL, t(8;21), inv(16)/t(16;16) 1
• Adverse risk: Complex karyotype, monosomy 5/7 1

Molecular Genetic Testing

For ALL patients with suspected/confirmed AML, mandatory testing includes:

• FLT3-ITD (strong recommendation—required for eligibility for targeted therapy with midostaurin) 1, 5
• NPM1, CEBPA, and RUNX1 mutations (for non-favorable risk AML) 1

Additional prognostic molecular testing should include:

• IDH1, IDH2, TET2, WT1, DNMT3A, TP53 1, 3
• KIT mutations for core binding factor AML (adults: strong recommendation; pediatrics: may perform) 1

For suspected APL specifically:

• Rapid PML-RARA detection (strong recommendation due to treatment urgency) 1
• Coagulation studies (PT, PTT, fibrinogen, D-dimer) to evaluate for disseminated intravascular coagulation 1

For ALL patients:

• Adults with B-ALL: BCR-ABL1 testing is mandatory (strong recommendation) 1, 6
• Pediatric B-ALL: ETV6-RUNX1, BCR-ABL1, KMT2A translocations, iAMP21, trisomy 4 and 10 1
• Additional mutations: PAX5, JAK1, JAK2, IKZF1 for B-ALL; NOTCH1, FBXW7 for T-ALL 1

FISH Testing

Should be performed as appropriate based on suspected subtype, but does not replace conventional karyotyping 1

Additional Required Studies

Cerebrospinal Fluid Evaluation

• Mandatory for ALL patients receiving intrathecal therapy: Cell count, cytocentrifuge preparation with blast enumeration reviewed by pathologist 1, 3
• May be obtained for other acute leukemia patients when clinically indicated and no contraindication exists 1

Imaging Studies

• CT chest/abdomen/pelvis to document lymphadenopathy, organomegaly, and extramedullary disease 7, 3
• Echocardiography for patients with cardiac risk factors or history of heart disease (required before anthracycline therapy) 1

Laboratory Studies

• Complete blood count with differential and peripheral blood smear review 3
• Comprehensive metabolic panel, lactate dehydrogenase, uric acid, phosphate 3
• Coagulation panel (especially critical before central line placement and if APL suspected) 1, 8
• HLA typing of patient and family members if allogeneic transplant candidate 1

Specimen Handling and Storage

The provider should ensure:

• Cryopreservation of cells or nucleic acid for future molecular/genetic studies 1, 3
• Samples stored under appropriate conditions in a laboratory compliant with regulatory/accreditation requirements 1
• Molecular testing performed at a cancer center or university-based hospital when possible 3

Alternative specimen types may be used when validated: Formalin-fixed paraffin-embedded tissue, unstained marrow/blood smears for molecular studies 1

Timeline Expectations

Advocate for:

• Preliminary report with basic diagnostics within 48-72 hours 3
• Complete final comprehensive report within 1-2 weeks when all ancillary results available 3

Critical consideration: For suspected APL, rapid PML-RARA testing results are needed urgently because treatment with all-trans retinoic acid (ATRA) should begin immediately given the high risk of fatal hemorrhage 1. Standard turnaround time should not delay APL-directed therapy.

Extramedullary Disease

If extramedullary disease presents without bone marrow/blood involvement:

• Tissue biopsy must be processed for morphologic, immunophenotypic, cytogenetic, and molecular genetic studies exactly as recommended for bone marrow 1
• Additional biopsies may be needed to obtain fresh material for ancillary testing 1

Key Pitfalls to Avoid

Insufficient sample collection: Ensure adequate volume is obtained initially to avoid repeat procedures that delay diagnosis and treatment 1

Relying on FISH/molecular testing without karyotype: Conventional cytogenetics provides genome-wide assessment and identifies unexpected abnormalities 1

Inadequate flow cytometry panel: Must be comprehensive enough for both initial diagnosis AND future MRD monitoring 1, 4

Delayed APL workup: If morphology suggests APL (M3 subtype with Auer rods), coagulation studies and rapid PML-RARA testing must be prioritized [1, @18@]