Diagnostic Tests for Lymphoma
The definitive diagnosis of lymphoma requires an excisional or incisional lymph node biopsy, as fine-needle aspiration alone is inadequate for initial diagnosis. 1, 2
Biopsy Requirements
- Preferred method: Excisional lymph node biopsy (complete removal of lymph node)
- Alternative when excision not possible: Incisional biopsy (partial removal)
- Limited role: Core needle biopsy only when excisional/incisional biopsy not feasible or to document relapse
- Inadequate: Fine-needle aspiration (FNA) alone is not suitable for initial diagnosis
The biopsy specimen should be:
- Sent fresh and intact
- Never immersed unsectioned in fixative
- Properly labeled with patient information and anatomic site
- Preserved for ancillary studies 2
Essential Pathologic Assessment
Immunohistochemistry
- Minimum panel for all lymphomas: CD45 (LCA), CD20, CD3 1
- Additional for B-cell lymphomas: CD10, BCL2, BCL6, Ki-67, CD138, kappa/lambda, HHV8 1
- For Hodgkin lymphoma: CD3, CD15, CD20, CD30, CD45, CD79a, PAX5 1
Flow Cytometry
- Kappa/lambda, CD45, CD3, CD5, CD19, CD10, TdT, CD14, CD20 1
Molecular/Genetic Testing (when indicated)
- Antigen receptor gene rearrangements
- Cytogenetics or FISH for specific translocations (BCL2, BCL6, MYC) 1
- EBER-ISH (Epstein-Barr virus) 1
Imaging Studies
Initial Staging
- PET-CT scan: From skull base to mid-thigh (or vertex to feet in selected cases) 1, 2
- Contrast-enhanced CT: Neck, chest, abdomen, and pelvis 1, 2
- Chest X-ray: Encouraged in cases with large mediastinal mass 1
PET-CT is superior to conventional CT for detecting nodal and extranodal involvement and is essential for initial staging and evaluating residual masses after treatment 1, 2.
Laboratory Tests
Essential Tests
- Complete blood count with differential and platelets
- Lactate dehydrogenase (LDH)
- Comprehensive metabolic panel
- Uric acid
- Hepatitis B and C testing
- HIV testing 1, 2
Additional Tests When Indicated
- Erythrocyte sedimentation rate (ESR)
- Beta-2-microglobulin
- Protein electrophoresis
- Cardiac function assessment (MUGA scan/echocardiogram) if anthracycline therapy planned 1, 2
Special Assessments
Bone Marrow Evaluation
- Bone marrow biopsy ± aspirate 1
- May be omitted if PET scan is negative or shows homogeneous bone marrow uptake 1
- Bone marrow involvement can be assumed if PET scan shows ≥3 skeletal lesions 1
CNS Evaluation
- Lumbar puncture with cytology and flow cytometry for high-risk patients 1
- Consider prophylactic intrathecal therapy in high-risk patients 1
Clinical Evaluation
- Document presence/absence of B symptoms:
- Fever >38.3°C (101°F)
- Drenching night sweats
- Unexplained weight loss >10% in 6 months 1
- Physical examination of all lymph node regions, spleen, and liver 1, 2
- Performance status assessment 1
Staging and Risk Assessment
- Ann Arbor classification system for staging 1, 2
- International Prognostic Index (IPI) or age-adapted IPI for risk stratification 1, 2
- Follicular Lymphoma International Prognostic Index (FLIPI) for follicular lymphoma 2
Common Pitfalls to Avoid
- Relying on FNA alone: This is inadequate for initial diagnosis and subtyping
- Delaying biopsy: Perform biopsy before initiating any therapy
- Inadequate tissue handling: Ensure proper preservation for all necessary studies
- Overlooking PET-CT false positives: PET scans may be positive in sites of infection or inflammation
- Missing high-risk features: Ensure proper risk stratification using prognostic indices
- Neglecting hepatitis testing: Essential before rituximab therapy due to reactivation risk
By following this comprehensive diagnostic approach, clinicians can accurately diagnose lymphoma and determine the appropriate subtype, which is essential for selecting optimal treatment strategies and improving patient outcomes.