Chronic Lymphocytic Leukemia Diagnosis and Management

Diagnostic Criteria

• The diagnosis of Chronic Lymphocytic Leukemia (CLL) requires ≥5 × 10^9/L B lymphocytes in peripheral blood and flow cytometry showing CD5+/CD19+/CD23+ phenotype, as recommended by the International Society of Hematology and the International Workshop on Chronic Lymphocytic Leukemia 1, 2
• Morphologically, CLL cells appear as small, mature-appearing lymphocytes with narrow cytoplasm and dense nucleus, and patients may present with markedly elevated leukocyte counts 3
• A complete blood count (CBC) with differential should be performed to quantify absolute lymphocyte count (ALC) and assess other cell lines for abnormalities, and a peripheral blood smear should be reviewed for morphologic features, as recommended by the American Society of Hematology and the College of American Pathologists 1, 2, 4

Disease Monitoring and Treatment Decisions

• Progressive lymphocytosis (increase >50% over 2 months or lymphocyte doubling time <6 months) is one criterion for initiating treatment, and the absolute lymphocyte count alone should not be used as the sole indicator for treatment 1
• Indications for treatment include progressive marrow failure, massive or progressive splenomegaly, massive or progressive lymphadenopathy, progressive lymphocytosis, autoimmune complications, and constitutional symptoms 1

Clinical Presentation and Evaluation

• Lymphocytosis is defined as a lymphocyte percentage >15% of the total white blood cell differential count, with relative lymphocytosis having a normal absolute lymphocyte count and absolute lymphocytosis having an increased absolute lymphocyte count (>4,000 lymphocytes/μL in adults) 1, 2, 5
• The following lymphocyte percentages suggest specific diagnoses:

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• Persistent lymphocytosis (>4 weeks), presence of lymphadenopathy or organomegaly, abnormal lymphocyte morphology, and age >50 years with persistent relative lymphocytosis ≥50% should raise suspicion for malignancy 1, 2
• HIV testing is mandatory, and viral hepatitis panel (HBV, HCV) and EBV and CMV testing should be performed, particularly if fever is present, as recommended by the Centers for Disease Control and Prevention 2, 6

Diagnostic Testing

• Flow cytometry immunophenotyping should be performed if malignancy is suspected, including T-cell markers (CD3, CD4, CD8), B-cell markers (CD19, CD20, CD23), NK cell markers (CD16, CD56), and clonality assessment (kappa/lambda light chains) 1, 4
• Bone marrow aspirate and biopsy are indicated when peripheral blood findings suggest malignancy 2, 1
• Cytogenetic studies, including FISH analysis for common abnormalities (del13q, del11q, del17p, trisomy 12), and molecular studies, including IgVH mutational status and ZAP-70 expression, should be performed, as recommended by the National Comprehensive Cancer Network 1

Treatment Response Evaluation

• Complete remission requires peripheral blood lymphocytes below 4 × 10^9/L (4,000/μL), partial response includes ≥50% reduction in peripheral blood lymphocyte count, and progressive disease includes ≥50% increase in lymphocyte count 1