Haem: Lymphoma Flashcards
Lymphoma vs Leukaemia
Lymphoma –> usually originates in lymph nodes or the spleen and spreads through the lymphatic system - hence malignant blood cells are predominantely found in the lymph nodes.
Leukaemia –> tends to originate in bone marrow resulting in bone marrow infiltration and malignant cells spread through blood stream
This distinction is seen in early stages - at later stages of both cancers, malignant cell location becomes less distinctive.
Define lymphoma
Neoplastic tumour of lymphoid cells that arise in and involve lymphoid tissues. Malignant cells are usually found in:
- Lymph nodes and lymphatic system
- Lymphoid organs (spleen, gut-assocaited lymphoid tissue, bone marrow)
- Skin (often T cell disease)
Malignant lymphoid cells are rarely found elsewhere CNS, Ocular, testes, breast etc
Types of lymphoid malignancies
Acute lymphoblastic leukaemia (ALL)
Non-Hodgkin Lymphoma (B-cell lineage)
Non-Hodgkin Lymphoma (T-cell lineage)
Hodgkin Lymphoma
Differentiate between Hodgkin’s and Non-Hodgkin’s Lymphoma
If there is a presence of Reed Sternberg cells (abnormal form of a B lymphocyte) = Hodgkin’s Lymphoma
Hodgkins lymphoma tends to only affect one or two lymph node groups.
Outline the difference in prevalence of Hodgkin’s lymphoma and Non-Hodgkin lymphoma.
- NHL = 80%
- Hodgkin = 20%
Outline the processes by which immunoglobulins and T cell receptors become capable of identifying a wide variety of antigens.
- The germline VDJ genes undergo recombination in the bone marrow to generate a wide repertoire of specificities.
- In germinal centres, a second stage of DNA alteration involving isotype switching and somatic hypermutation (point mutations) generates even more diversity.
What is the main downside of the processes that generate variety in immunoglobulins and TCR?
- Recombination errors and new point mutations can occur resulting in predisposition to malignancies
- Lymphocytes are reliant on apoptosis to keep their massive proliferation under control (90% of lymphocytes die in the germinal centre)
- If a mutation turns off apoptosis, it can lead to malignancy or autoimmunity
- There is rapid cell proliferation in germianl centres which increase risk of replication errors
Outline how chromosomal translocations in B cells can lead to malignancy.
a
List some oncogenes that are implicated in lymphoma/leukaemia.
- Bcl2
- Bcl6
- Cyclin D1
- c-Myc
These are anti-apoptotic or proliferative.
List some risk factors that contribute to the aetiology of lymphoma.
- Constant antigenic stimulation
- Infections
- Loss of T cell function
List some examples of how constant antigenic stimulation can lead to lymphoma.
- H. pylori → gastric MALT marginal zone B-cell NHL of the stomach
- Sjogren syndrome → marginal zone B-cell NHL of the parotid
- Coeliac disease → small bowel T cell lymphoma, enteropathy-associated T cell NHL
List two examples of viral infections that can lead to lymphoma.
Direct viral integration: HTLV1
- HTLV1 infects T cells by vertical transmission
- May cause adult T cell leukaemia/lymphoma (very aggressive)
- Caused by viral genome integrating into T cell genome and driving proliferation
EBV infection and immunosuppression
- EBV established latent infection in B cells which is kept in check by cytotoxic T cell (kill EBV antigen-expressing B cells)
- Loss of T cell function (e.g. HIV, post-transplant immunosuppression) can lead to EBV-driven lymphoma
List some different types of tissues of the lymphoreticular system.
- Generative tissue: bone marrow and thymus (generates or matures lymphoid cells)
- Reactive tissue: lymph nodes and spleen (development of immune reaction)
- Acquired tissue: extra-nodal lymphoid tissue (e.g. skin, stomach, lung - responsible for developing a local immune response)
List the different cell types of the lymphoreticular system.
Lymphocytes
* B cells (express surface Ig + Ab production)
* T cells (surface TCR, regulate B cells, Cytotoxic)
Accessory cells
* Antigen-presenting cells
* Macrophages
* Connective tissue cells
Describe the normal histological appearance of a lymph node.
- These are rounded areas full of B cells (B cell follicles)
- The mantle zone is a crescent-shaped region where naïve unstimulated B cells are found
- These naïve B cells will eventually migrate into the germinal centre, and mature B cells will end up in the medulla (middle of rounded follicles)
- T cells are found in T cell areas surrounding the B cell follicles
Describe the composition of T cell areas in lymph nodes.
- Consists of lots of T cells, antigen-presenting cells and high-endothelial venules
- This is the site where T cells bind to antigens and are selected/activated
What is the main technique used to identify different types of lymphocyte within a lymph node biopsy?
Immunohistochemistry
What are the main markers used for B and T cells?
T cell = CD3, CD5
B cell = CD19, CD20
Which factors are taken into account when classifying a lymphoma?
- Clinical
- Histological
- Immunohistochemical
- Molecular
What constitutional symptoms may be present in a patient with lymphoma?
Painless enlargement of lymph nodes
B symptoms - fever, night sweats, weight loss
Pruritis
Outline the WHO classification of lymphoma.
Hodgkin lymphoma
- Classical
- Lymphocyte predominant
Non-Hodgkin lymphoma
- B cell (MOST COMMON)
- Precursor B cell neoplasm
- Peripheral B cell neoplasm (low and high grade)
- T cell
- Precursor T cell neoplasm
- Peripheral T cell neoplasm
Why is non-Hodgkin lymphoma often disseminated at presentation?
Neoplastic lymphoid cells circulate in the blood leading to disseminated disease at presentation. Hodgkins lymphoma is an exception because it tends to only affect one or two lymph node groups.
NOTE: lymphoid neoplasms can disrupt normal immune functioning leading to immunodeficiencies
What are the diagnostic tools used by pathologists when investigating lymphoma?
Cytology (from aspiration)
Histology
* (architecture: nodular, diffuse
* Cells: small round, small cleaved, large
Immunohistochemistry (identify proteins on/in cells - i.e. determine cell lineage)
* cell types (CD markers)
* Cell distribution
* Loss of normal surface proteins
* Expression of abnormal proteins (e.g. cyclin D1 indicative of Mantle cell lymphoma)
Cytogenetics
* FISH - identify chromosome translocations
* PCR - identify chromosome translocations, cloncal T cell receptor or Ig gene rearrangement
Which molecular tools are used when investigating lymphoma?
- FISH - identify chromosomal translocations
- PCR - identify chromosomal translocations, clonal T cell receptor of Ig gene rearrangement
Give an example of a chromosomal translocation that is diagnostic of lymphoma.
11;14 = Mantle Cell Lymphoma
Give an example of a chromosomal translocation that is prognostic in lymphoma.
2;5 = anaplastic large cell lymphoma
Which type of scan is often used to stage lymphoma?
FDG-PET/CT
Key differences between HL and NHL
- Hodgkin is more localised (usually one nodal site)
- Hodgkin spreads contiguously to adjacent to adjacent lymph nodes while NHL tends to involve multiple lymph node sites and spread continuously
List the different types of HL
Classical HL:
- Nodular sclerosing (commonest)
- Mixed cellularity
Lymphocyte predominant
Outline the typical presentation of classical Hodgkin lymphoma.
- Young and middle-aged patients with only a single group of lymph nodes involved
- Associated with EBV