Diffuse large B cell lymphoma, Burkitt lymphoma

A) Diffuse Large B-Cell Lymphoma (DLBCL)

Overview

• Most common type of lymphoma in adults
• Aggressive (high-grade), fast-growing B-cell lymphoma

Pathogenesis

• Frequent gene mutations:
  • BCL6 gene rearrangements
  • t(14;18) → BCL2 overexpression
  • Loss-of-function mutations
• Two subtypes by cell of origin:
  • GCB type (germinal center B-cell origin)
  • ABC type (activated B-cell origin) — worse prognosis

Morphology

• No follicular pattern — diffuse proliferation of large cells
• Two main cell types:
  • Centroblasts: large cells seen in reactive follicles
  • Immunoblasts: antigen-activated lymphocytes, normally in paracortex
• Occasional large anaplastic cells
• High mitotic activity

Clinical features

• Any age; peak at 60 years
• Rapid lymph node enlargement
• Frequent extra-nodal manifestation: GI-tract, mediastinum, CNS
• Without treatment: aggressive and fatal
• With anti-CD20 (rituximab/MabThera): ~50% curable

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B) Burkitt Lymphoma

Overview

• Aggressive (high-grade), fast-growing B-cell lymphoma
• Subtypes:
  • Endemic (African): affects children; jaw tumors
  • Sporadic (Europe/North America): children and young adults; abdominal tumors
  • Post-transplant/immunodeficient: essentially HIV patients

Pathogenesis

• t(8;14) → fuses MYC gene to IgH → MYC overexpression → massive cell proliferation
• EBV infection plays a pathogenic role → expands B-cell pool → increases risk of malignant transformation

Morphology

• Neoplastic cells are molded against each other
• Round/oval nuclei with several nucleoli; basophilic cytoplasm containing lipid vacuoles
• Very high proliferation rate → numerous mitotic figures and apoptotic bodies
• Tingible-body macrophages phagocytose apoptotic debris → surrounded by clear space → “starry sky” appearance

Clinical features

• Aggressive tumor with rapid growth
• Mostly children or young adults
• Extra-nodal manifestation:
  • Maxilla and mandible → Endemic type
  • Abdomen → Sporadic type
• Leukemic manifestation may occur
• Intensive chemotherapy → potentially curable

💡 High-yield: DLBCL = most common adult lymphoma; aggressive; BCL6/BCL2; ~50% curable with anti-CD20. Burkitt = t(8;14)/MYC overexpression; EBV association; starry sky pattern; lipid vacuoles in cytoplasm; Endemic → jaw; Sporadic → abdomen.