WHERE TO START?
I. Consider the immune system organ by organ:
– Lymph nodes; Bone marrow; Spleen; Thymus; Mucosa Associated Lymphoid Tissue
II. For each organ, ask some questions:
– We will focus on lymphoid tissues here – specifically diseases of lymph nodes
– This is a systematic approach.and you can do the same with the other tissues of the haematolymphoid system.
Diseases of Lymph Nodes:
- Cells (B, T, NK cells)
- Tissues / Organs
- Primary lymphoid organs (bone marrow, thymus)
- Secondary lymphoid organs (lymph nodes, MALT, spleen, etc…)
- The main functions of lymphoid cells are defensive – as part of the adaptive immune response (B and T cells) an innate immunity (NK cells). Revise the physiology of blood lectures.
- What happens if there is over-, under- or inappropriate immune response?
- You will find some answers in your Immunology lecture notes
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- Reactive – eg. Reactive lymphoid hyperplasia (lymph nodes, thymus, MALT)
- Inflammatory / Infectious – eg. Tuberculosis involving lymph nodes
- Neoplastic
- Neoplasms of the lymphoid tissue are usually malignant
- Simplest classification is: Primary vs Secondary
- Lymphomas
- Leukaemias
- Some neoplasms can affect BOTH the lymph nodes and the bone marrow. You must have heard of the terms "Lymphom" and "Leukaemia". Do you know the difference? Click on the tab below to see the explanation.
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Lymphomas refer to haematopoietic malignancies that arise predominantly as masses, either in lymph nodes or in extranodal locations.
Leukaemias refer to haematopoietic malignancies that present with widespread involvement of the bone marrow and often the peripheral blood as well.
This distinction applies mainly to lymphoid malignancies. – because myeloid neoplasms usually do not involve lymph nodes.
Among the lymphoid neoplasms, many of them present mainly as lymphomas (i.e. nodal or extranodal masses). There are several lymphoid neoplasms, however, that also can present as leukaemias. Thus, these neoplasms are often given the name "…… lymphoma/leukaemia", and they are diagnosed as leukaemia if marrow and/or peripheral blood examination reveals the presence neoplastic lymphoid cells in at least specific quantities.
Eg. Small lymphocytic lymphoma(SLL)/ Chronic lymphocytic leukaemia (CLL)
This is diagnosed as SLL if the main clinical presentation is lymphadenopathy without significant marrow disease, while it is diagnosed aas CLL if the peripheral blood absolute lymphocyte count exceeds a certain value.
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- What is a simple classification system for lymphomas?
- First step: Hodgkin vs Non-Hodgkin Lymphoma
- Second step: NHL –> WHO Classification – B vs T cell; Immature vs Mature
- Your lecture notes provide a good overview of the classification system
The next question is:
4. How do these main lymphoid pathologies manifest themselves clinically?
This will be answered in the next page. Click on the “Clinicopathologic Correlation” button below.