Leukemias and Lymphomas
Classification, Etiology, Pathogenesis, and Clinical Manifestations
Leukemia: A group of malignant neoplasms of blood-forming tissues, characterized by abnormal proliferation of leukocytes in bone marrow and blood.
Lymphoma: Malignant tumors arising from lymphoid tissue, mainly affecting lymph nodes and sometimes spreading to other organs.
Classification
Leukemias
By cell line:
Lymphomas
Etiology
Shared Causes:
- Genetic mutations: (e.g., Philadelphia chromosome in CML → BCR-ABL fusion gene).
- Radiation exposure
- Chemicals: Benzene, alkylating agents.
- Viruses:
- EBV → Burkitt lymphoma, Hodgkin lymphoma.
- HTLV-1 → adult T-cell leukemia / lymphoma.
- HIV → increases risk for NHL.
- Immunodeficiency: Congenital or acquired.
- Autoimmune diseases (esp. linked to some NHL types).
Pathogenesis
Leukemia
- Mutation in hematopoietic stem cells → uncontrolled clonal proliferation.
- Bone marrow crowding:
- Normal cell lines suppressed → anemia, thrombocytopenia, neutropenia.
- Spillover into blood → high WBC count (but often dysfunctional).
- Infiltration into tissues → liver, spleen, CNS, skin.
Lymphoma
- Malignant transformation of lymphocytes (mostly B- cells).
- Accumulation in lymphoid tissue (lymph nodes, spleen).
- May spread hematogenously to liver, bone marrow, GI tract, CNS.
- In HL: Reed-Sternberg cells release cytokines → recruit inflammatory cells → lymphadenopathy and systemic symptoms.