P03.012 Lymphoma

Lymphomas are a heterogeneous group of cancers arising from lymphocytes, a type of white blood cell. Understanding these malignancies is crucial for the PLAB exam, as they represent a significant portion of hematologic malignancies encountered in clinical practice. This guide provides a concise overview of lymphomas for PLAB preparation.

Classification:

The World Health Organization (WHO) classification system categorizes lymphomas based on their cell of origin (B-cell or T-cell) and growth pattern (Hodgkin lymphoma or non-Hodgkin lymphoma). This distinction is essential for diagnosis, prognosis, and treatment selection.

Key Points to Remember:

• Origin:
  • B-cell lymphomas are more common than T-cell lymphomas.
  • B-cell lymphomas can sometimes produce antibodies (immunoglobulins), known as monoclonal gammopathy.
• Growth Pattern:
  • Hodgkin lymphoma (HL) is characterized by the presence of Reed-Sternberg cells.
  • Non-Hodgkin lymphoma (NHL) is a more diverse group with various subtypes.

Non-Hodgkin Lymphoma (NHL):

• More common than Hodgkin lymphoma.
• Subtypes can be further categorized based on growth rate (aggressive vs. indolent).
• Common subtypes include:
  • Diffuse large B-cell lymphoma (DLBCL): An aggressive lymphoma.
  • Follicular lymphoma: An indolent lymphoma.
  • Mantle cell lymphoma: An aggressive lymphoma.
  • Burkitt lymphoma: A highly aggressive lymphoma.

Hodgkin Lymphoma (HL):

• Less common than NHL.
• Subtypes are classified based on the presence or absence of specific lymphocyte characteristics.
• Common subtypes include:
  • Classical Hodgkin lymphoma: Further subdivided based on lymphocyte predominance.
  • Nodular Lymphocyte-Predominant Hodgkin Lymphoma (NLPHL): A more indolent form.

Clinical Presentation:

• Lymphadenopathy (painless or painful lymph node enlargement) is a common presenting feature.
• Other symptoms may include:
  • Fever
  • Night sweats
  • Unexplained weight loss
  • Fatigue
  • Pruritus (itching)

Diagnosis:

• Clinical history and physical examination.
• Blood tests, including complete blood count (CBC) and lactate dehydrogenase (LDH).
• Lymph node biopsy with immunohistochemistry to identify specific cell markers.
• Imaging studies like CT scan or PET scan to assess disease extent.
• Bone marrow biopsy may be required in some cases.

Treatment:

Treatment for lymphomas depends on the specific subtype, stage (extent of disease), and patient factors. Common treatment modalities include:

• Chemotherapy: Combination chemotherapy regimens are frequently used.
• Radiotherapy: Can be curative or used in combination with chemotherapy.
• Immunotherapy: Monoclonal antibodies and immune checkpoint inhibitors are playing an increasingly important role.
• Stem cell transplantation: For certain aggressive lymphomas.

Exam Keep Points:

• Be familiar with the WHO classification of lymphomas.
• Recognize the key features of Hodgkin lymphoma (Reed-Sternberg cells) and differentiate it from non-Hodgkin lymphoma.
• Understand the common subtypes of NHL and their general aggressiveness.
• Identify the cardinal symptoms of lymphoma (lymphadenopathy, B symptoms).
• Outline the diagnostic approach to suspected lymphoma, including biopsy and immunohistochemistry.
• Be aware of the main treatment modalities for lymphomas (chemotherapy, radiotherapy, immunotherapy).

Additional Resources:

• National Cancer Institute (NCI): https://www.cancer.gov/types/lymphoma/hp
• Lymphoma Association: https://lymphoma-action.org.uk/
• Royal College of Pathologists: https://www.rcpath.org/asset/DE0B5B4A-7F77-4FE2-AB56FD618EE69098/