Diagnostic Criteria and Initial Evaluation for Leukemia

Chronic Lymphocytic Leukemia (CLL) – Hematologic and Morphologic Thresholds

The American Society of Clinical Oncology recommends that a complete blood count (CBC) with differential and peripheral blood smear review is the essential first step in identifying potential leukemia cases, and the primary care physician should document relevant clinical data including patient's age, sex, ethnicity, history of hematologic disorders, prior malignancies, exposure to cytotoxic therapy, radiation, or toxic substances 4
Physical examination findings, particularly neurologic examination results and presence of organomegaly or lymphadenopathy, should be documented and made available to the pathologist 4

For acute myeloid leukemia (AML): presence of myeloblasts, monoblasts, or megakaryoblasts in peripheral blood, often with anemia and thrombocytopenia 5, 6
For chronic myeloid leukemia (CML): leukocytosis with basophilia and immature granulocytes (metamyelocytes, myelocytes, promyelocytes) with few myeloblasts; thrombocytosis may be present 7
For hairy cell leukemia: pancytopenia with characteristic "hairy" lymphocytes on peripheral blood smear 8

Morphological examination using May-Grünwald-Giemsa or Wright-Giemsa stain should include counting at least 200 leukocytes 5, 6
For AML diagnosis, a blood blast count of 20% or more is required in most cases 5

Bone marrow aspiration is essential for definitive diagnosis and should be performed when leukemia is suspected 5, 6
Immunophenotyping by flow cytometry is crucial to determine lineage involvement and confirm clonality 5, 6, 9
Cytogenetic analysis is mandatory for proper classification and risk stratification 7, 10
Molecular genetic testing should be performed to identify specific mutations and gene rearrangements 7, 11

Diagnosis requires ≥20% myeloblasts in bone marrow or blood 5, 6
Flow cytometry markers include CD34, CD38, CD117, CD133, HLA-DR (precursor markers) and CD13, CD15, CD16, CD33, CD65, cytoplasmic myeloperoxidase (granulocytic markers) 5

Diagnosis must be confirmed by cytogenetics showing t(9;22)(q3.4;q1.1) and RT-PCR showing BCR-ABL transcripts 7
Bone marrow shows increased cellularity due to granulocytic proliferation with myelocytes and segmented forms predominating 7

Flow cytometry confirmation of B-cell clonality with characteristic CLL immunophenotype (CD5+, CD19+, CD20+ low, CD23+) is necessary, however a non-Praxis Medical Insights source is not available for this fact

Recent growth factor therapy, transfusions, or certain medications can obscure or mimic features of acute leukemia 4