Can you explain Burkitt lymphoma?

Burkitt Lymphoma Overview

Burkitt lymphoma (BL) is a highly aggressive, rapidly proliferating mature B-cell non-Hodgkin lymphoma characterized by MYC gene translocation, extremely high proliferation rates (>95% Ki-67 positivity), and a distinctive "starry sky" histologic appearance—it is the fastest growing human tumor but remains highly curable with intensive chemo-immunotherapy, particularly in children and young adults. 1

Epidemiology and Clinical Variants

BL exists in three epidemiologic forms that differ by geography, viral associations, and presentation sites 1:

Endemic BL

• Occurs primarily in equatorial Africa, South America, Turkey, and Papua New Guinea
• Associated with Epstein-Barr virus (EBV) in ~95% of cases
• Strongly linked to malaria infection
• Accounts for up to 70% of childhood cancers in malaria-endemic regions of equatorial Africa
• Typically presents in the jaw, orbit, mesentery, and central nervous system (CNS)

Sporadic BL

• Predominates in North America and Europe
• Only ~15% are EBV-positive
• Commonly presents in the abdomen, lymph nodes, bone marrow, or cerebrospinal fluid (CSF)
• Represents the most common form in high-income countries

Immunodeficiency-Associated BL

• Occurs primarily in HIV-infected patients
• May be the initial AIDS-defining condition
• Up to 70% test positive for EBV

Important caveat: Recent genomic studies have refined this classification, identifying EBV-positive and EBV-negative molecular subtypes that cut across traditional epidemiologic categories and exhibit distinct biological profiles 2.

Pathologic and Diagnostic Features

Morphology

BL has distinctive microscopic characteristics 1:

• Cytology: Intermediate-sized lymphoid cells (similar to histiocyte nucleus size) with round nuclei, coarse chromatin, multiple small nucleoli, and scant cytoplasm
• Tissue architecture: Patternless sheets of cells with pseudo-cohesion (cells appear to mold to one another)
• "Starry sky" appearance: Scattered tingible-body macrophages containing apoptotic debris, reflecting the extremely high cell turnover rate
• Clear cytoplasmic vacuoles may be visible on Wright-Giemsa staining

Immunophenotype

Essential markers for diagnosis 1:

• Positive: CD20, CD10 (germinal center marker), BCL6, surface immunoglobulin
• Negative: BCL2, terminal deoxynucleotidyl transferase (TdT), CD3
• Ki-67: ≥95% positive (critical diagnostic feature)

Cytogenetics

MYC translocation is the hallmark genetic abnormality 1:

• BL exhibits a simple karyotype with MYC translocation involving an immunoglobulin gene as the sole abnormality
• Most commonly t(8;14), but also t(2;8) or t(8;22)
• Fluorescence in situ hybridization (FISH) for C-MYC rearrangement is essential for diagnosis

Critical distinction: Double-hit and triple-hit lymphomas (MYC plus BCL2 and/or BCL6 rearrangements) are rare in pediatric BL but more common in adolescent/young adult patients. However, these are treated with the same intensive regimens as standard BL in the pediatric population 1.

Clinical Presentation and Workup

Common Presentations

• Rapidly progressive abdominal masses (sporadic form)
• Jaw or facial masses (endemic form)
• B symptoms (fever, night sweats, weight loss)
• High tumor burden with risk of tumor lysis syndrome
• CNS involvement in ~9% of pediatric patients at presentation 1

Required Diagnostic Workup 1

Essential evaluations:

• Excisional or incisional biopsy (preferred over FNA alone)
• History and physical examination focusing on node-bearing areas, liver/spleen size
• Complete blood count with differential and platelets
• Comprehensive metabolic panel (assess for tumor lysis)
• LDH (prognostic marker)
• Bilateral bone marrow aspirate and biopsy
• Lumbar puncture with CSF cytology
• FDG-PET/CT or FDG-PET/MRI (if available, but don't delay treatment)
• High-resolution CT or MRI
• Baseline echocardiogram or MUGA scan
• Hepatitis B testing
• Pregnancy testing in women of childbearing age
• Fertility counseling with preservation options

Important pitfall: Treatment should not be delayed for complete diagnostic workup if the patient is critically ill. Morphology and flow cytometry are the minimum requirements to begin treatment 1.

Prognosis and Treatment Outcomes

Survival Rates

The prognosis varies dramatically by geography and resources 1, 2:

• High-income countries: 80-90% overall survival in children and young adults with intensive chemo-immunotherapy
• Sub-Saharan Africa: Survival rarely exceeds 50% due to diagnostic delays, limited treatment access, and inadequate supportive care
• Pediatric NHL overall: 5-year relative survival of 91% (age ≤14) and 88% (age 15-19) 1

Poor Prognostic Features

• Advanced stage (III-IV)
• Elevated LDH
• CNS involvement
• Bone marrow involvement
• Elderly age
• Relapsed or refractory disease 3

Treatment Principles

BL requires immediate intensive multiagent chemotherapy with anti-CD20 monoclonal antibody therapy (rituximab) 4, 5. Treatment is complex and should preferably occur at centers with expertise in managing these aggressive lymphomas 1.

Key Treatment Considerations

• Tumor lysis syndrome prophylaxis: Critical given the extremely high proliferation rate and chemosensitivity
• CNS-directed therapy: Required due to high risk of CNS involvement
• Dose-dense regimens: Multiple intensive cycles delivered in rapid succession
• Supportive care: Essential for successful outcomes, including management of neutropenic fever, mucositis, and metabolic complications

Unmet Needs

• Optimal therapy for elderly patients remains undefined
• Treatment of CNS-involved disease needs improvement
• Relapsed/refractory disease has poor outcomes
• Novel approaches under investigation include bispecific antibodies, CAR-T cell therapy, and targeted agents 4, 5

Staging

The International Pediatric NHL Staging System (IPNHLSS) is now preferred over the older Murphy/St. Jude classification 1. This revised system better accounts for:

• Frequent involvement of skin, bone, kidney, and ovarian sites
• Improved detection of bone marrow and CNS disease
• Recognition of newer histologic entities

CNS positivity criteria (defines stage IV disease) 1:

• Any lymphoma cells in CSF by cytology
• Any CNS tumor mass by imaging
• Cranial nerve palsy (unexplained by extracranial tumor)
• Clinical spinal cord compression
• Parameningeal extension (cranial and/or spinal)