Lymph node pathology Flashcards
What are the Primary Lymphoid organs?
Thymus and bone marrow
What are the Secondary Lymphoid organs?
Spleen, lymph nodes, mucosa-associated lymphoid tissue
Describe the macroscopic appearance of a lymph node.
Oval shaped.
Well circumscribed.
Outer fibrous capsule.
Veins and arteries at the hilum of the node deliver blood.. Lymphatics also leave here
Where does lymph flow through a node, from afferent to efferent lymphatic duct?
Afferent vessels enter through the capsule, into subcapsular sinuses, cortical sinuses, run into the medulla, leave via efferent lymphatics at the hilum.
What are medullary cords?
Extensions of mainly T-cells in the medulla.
What are the three main regions into which the lymph node is divided? and which cells predominate in these areas?
Paracortex Primary follicle Mantle zone Medullary cords Sinuses
What will you find in the Paracortex?
Naive T cells
High endothelial venules
Interdigitating dendritic cells
What will you find in the Primary follicle?
Naive B cells
Follicular dendritic cells
T cells
What will you find in the mantle zone?
Naive B cells
What will you find in the medullary cords?
Small T and B lymphocytes
Immunoblasts
Plasma cells
What will you find in the sinuses?
Lymph
Macrophages
Small T and B lymphocytes
Eosinophils
What are the sinuses lined by?
Endothelial cells
What sort of immune response could be observed in the paler area of germinal centre?
Humoral immune response
Which cells are responsible for driving the differentiation of B cells into B effector cells?
Follicular dendritic cells and T cells
Where does the final differentiation of B cells occur?
In the medullary cords
What are B cells called as they leave the follicle? Why?
Immunoblasts.
Called this because they are immature - final differentiation in the medullary cords.
After appropriate stimulation, naive B lymphocytes will undergo clonal expansion and differentiate. Where does this take place? and what cells do they become?
Mantle zone.
Centrobasts - centrocytes - immunoblasts.
What are two broad categories of Lymphadenopathies?
“Reactive’ inflammatory and infection.
Neoplastic.
What sort of stimuli would cause Chronic non-specific lymphadenitis characterised by follicular hyperplasia?
Stimuli that activate humoral immune responses.
e.g. autoimmune disease, microbial infection.
What sort of Stimuli would cause Paracortical Chronic non-specific lymphadenitis?
Stimuli that activate cellular immune responses.
e.g. viral infections, certain drugs.
What are the characteristics of acute non-specific lymphadenitis?
Neutrophil infiltration, oedema, follicular hyperplasia, large and painful nodes.
What are three causes of neoplastic lymphadenopathy?
Primary Tumours, Secondary tumours, Leukaemic infiltration
Which is the most common cause of neoplastic lymphadenopathy?
Secondary tumours (metastases)
On which features is the classification and diagnosis of neoplastic proliferations of haematopoietic and lymphoid tissues based?
Cell lineage, morphology, immunophenotypic profiles +/- genetic abnormalities and to some extent clinical features
What is Leukaemia?
Malignant neoplastic proliferation of haematolymphoid cells, mostly at a precursor stage, usually neoplastic cells spill over into the blood +/- infiltrate other tissues.
What is the histological distinction between chronic and Acute leukaemia?
Chronic leukaemia usually involves abnormal cells with features of cells that are further along in the differentiation pathway than the blasts seen in acute leukaemia.
What is Lymphoma?
Primary malignant neoplastic diseases of lymphoid cells, mostly at a mature or post bone marrow stage (i.e. ‘peripheral’ as opposed to ‘precursor’).
Usually arise as more discrete masses in tissues outside of bone marrow, but can involve bone marrow.
What are the two main types of lymphoma?
Hodgkin and non-hodgkin
What is the chromosomal translocation seen in most follicular lymphomas?
t(14, 18)
BCL2 gene is translocated onto chromosome 14 at an immunoglobulin locus, which has a high rate of replication/transcription. This causes over-transcription of BCL2 gene, which is anti-apoptotic.
What is the translocation seen in Burkitt’s lymphoma?
Part of Chromosome 8, containing the MYC oncogene, is translocated onto one of 3 immunoglobulin gene regions on other chromosomes. This leads to overexpression of cMyc protein, and sustained growth promotion.
How does EBV cause lymphoma?
Infects B lymphocytes. Kept latent by T cell immunity. Loss of T-cell immunity allows expression of viral proteins, can lead to activation of signalling pathways, polyclonal B-cell proliferation and eventually lymphoma.
How is diagnosis of lymphoma most accurately achieved?
Tissue biopsy (rather than Fine Needle Aspiration)
What are the neoplastic cells involved in Hodgkin’s lymphoma? Describe.
Reed-Sternberg cells - Neoplastic germinal centre B-cells.
What are the histological features of Reed-Sternberg cells?
Large, abundant cytoplasm, large bilobate nucleus with prominent eosinophilic nucleoli.
What are the two main groups of non-hodgkin lymphomas
B-cell (85%) and T-cell
Where do Non-Hodgkin Lymphomas usually arise?
Lymphoid organs (e.g. lymph nodes) Many 'extranodal' - e.g. thyroid in Hashimotos, Stomach in H. pylori gastritis.
What type of Lymphoma is Follicular Lymphoma?
Non-Hodgkin (2nd most common)
What features are characteristic of Follicular lymphoma?
Shows features of differentiating B cells within a germinal centre. The predominant cell type shows features of centrocytes. Form nodules/follicles.
What is the most common type of non-hodgkin lymphoma?
Diffuse large B cell lymphoma
What are the characteristics of Diffuse large B cell lymphoma?
Recapitulate germinal centre or post germinal centre B cells (centroblasts and immunoblasts)
What are Follicular lymphomas usually positive for?
Bcl-2
Do follicular lymphoma cells expres surface immunoglobulin?
YES!
What are two examples of B-cell antigens?
CD19, CD20
What are the characteristics of Chronic lymphocytic leukaemia/small lymphocytic lymphoma?
Weak surface immunoglobulin.
Cells are mature looking B lymphocytes of naive or memory cell type.
Distinguished by presence of lymphocytosis.
What is the relationship between chronic lymphocytic leukaemia and small lymphocytic lymphoma?
Chronic lymphocytic leukemia (CLL) and small lymphocytic lymphoma (SLL) are B-cell lymphomas. CLL and SLL are essentially the same disease, the only difference being where the cancer primarily occurs. When most of the cancer cells are located in the bloodstream and the bone marrow, the disease is referred to as CLL, although the lymph nodes and spleen are often involved. When the cancer cells are located mostly in the lymph nodes, the disease is called SLL.
(Lymphoma Research Foundation)
