Lecture on Lymphomas and Leukemias

Introduction

• Series of lectures on lymphomas and leukemias.
• Discuss differences between lymphomas and leukemias before delving into details.

Key Definitions

• Lymphomas:
  • Solid, cohesive tumors of the immune system.
  • Typically originate from lymphoid tissue, but can occasionally originate from the CNS (e.g., in HIV/AIDS patients).
• Leukemias:
  • Malignancies of hematopoietic precursor cells (from the bone marrow).
  • Cells proliferate abnormally, spill into circulation, increasing total cell count in blood.
  • Do not form cohesive masses due to fewer adhesion molecules compared to lymphomas.

Distinction Between Lymphomas and Leukemias

• Traditional View:
  • Lymphomas and leukemias treated as completely separate categories.
• Modern View:
  • Some lymphomas can enter a leukemic phase and vice-versa.
  • Modern oncology shows the blurred lines between the two.
• Functional Characteristics:
  • Lymphomas: Solid masses.
  • Leukemias: Non-cohesive, spread in circulation.

Classification

• Lymphoid Neoplasms:
  • Derived from lymphoid or myeloid stem cells.
  • Can be lymphoid leukemias or myeloid leukemias.
• Stem Cells:
  • Lymphoid stem cells: Develop into B cells, T cells, and natural killer cells.
  • Myeloid stem cells: Develop into red blood cells, platelets, and other white cells (except lymphocytes).
• Prognosis and Treatment:
  • Modern focus is on identifying tumor cells as B cell or T cell, rather than their location.
  • Importance of karyotype and molecular abnormalities for treatment decisions.

Classification Systems

• Old Classification:
  • R.E.A.L. Classification: Revised European American Lymphoma classification.
• Current Classification:
  • WHO Classification of Lymphomas.
  • Divides lymphoid tumors into four categories:
    • Non-Hodgkin’s Lymphomas
    • Hodgkin’s Lymphomas
    • Lymphocytic Leukemias
    • Plasma Cell Dyscrasias

Summary of Tumor Types

• Lymphoid Tumors:
  • Non-Hodgkin’s Lymphomas: Solid cohesive tumors.
  • Hodgkin’s Lymphomas: Solid cohesive tumors.
  • Lymphocytic Leukemias: Derived from lymphocytes but spill into circulation.
  • Plasma Cell Dyscrasias: Derived from plasma cells.
• Further Studies:
  • Detailed exploration of non-Hodgkin’s and Hodgkin’s lymphomas.
  • Comparison between non-Hodgkin’s and Hodgkin’s lymphomas.