21. Benign Lymphoid Proliferations Flashcards
List the lymphoid organs
- lymph nodes
- spleen
- thymus
- bronchial associated lymphoid tissue (BALT)
- gastrointestinal associated lymphoid tissue (GALT)
- Waldeyer ring
Examples of primary lymphoid tissues
- T cells
- cell mediated immunity
- matured in thymus - B cells
- humoral immunity
- matured in bone marrow - Null cells
- not B or T cell marker responsive - NK cells
- may react with T cells
What is lymphopenia
abnormally low levels of lymphocytes
Causes of lymphopenia
- advanced HIV infection
- congenital immune deficiency syndrome
- steroid
- chemotherapeutic drugs
- autoimmune diseases
What is lymphocytosis
excessive level of lymphocytes
Causes of lymphocytosis
- viral infection (most often)
- infectious mononucleosis - bacterial infections (rare)
- whooping cough
- TB
- brucellosis
Type of lymphocytes in blood
- T lymphocyte
- B lymphocyte
- Null cells
- NK cells
How do we recognise lymphocytes as either T or B or null
immunohistochemistry or flow cytometry
Types of WBC neoplastic disorder
- leukemia
- cancer of bone marrow, blood, blast cells
- acute/chronic and myeloid/lymphoid
- if myeloid/lymphoid cells become malignant, it is known as ‘blasts’ - lymphomas
- lymph nodes, tumour
- Hodgkins, non-Hodgkins (myeloma) - premalignant conditions
- myeloproliferative syndrome
- myelodysplastic syndrome
Basic lymphocyte markers
- CD45 stains most lymphocytes
- T-lymphocyte - CD20, CD79
- B-lymphocyte - CD3, CD2, CD4, CD5, CD8
Explain T-cell cytotoxicity
- cytotoxic T-cell
- in infected cell, antigen associates with class I MHC molecule
- T cell recognises the combination - T helper cell
- in antigen presenting cell, antigen associates with class II MHC molecule
- helper T cell recognises the combination
- activate B cells
Explain B-cell immunity
- antigen recognition
- activation of B lymphocytes
- Proliferation
- differentiation
outcome:
a) antibody secretion by antibody secreting plasma ceells
b) isotope switching by IgG-expressing B cell
-IgM to IgG
c) Affinity maturation by high-affinity IgG-expressing B cell
d) memory B cell by high-affinity IgG-expressing B cell
Types of mononuclear phagocytic cells
- monocytes
- differentiate into macrophages - histiocytes
- phagocytosis and cytokine production - macrophage
- histiocytes with more phagocytic function - multinucleated giant cell
- dendritic cell
- antigen presenting cell to T cell - langerhan cell
- antigen presenting cell
What are the clinical signs of lymphoid tissue proliferation
- lymphadenopathy
- splenomegaly
- hepatomegaly
- thymic enlargement
- marrow expansion
- masses in naropharynx, GIT
Clinical features of lymphoid tissue proliferation
- Malignant
- single, firm, painless large node - Benign
- soft, tender node
Causes of an enlarged node
- Benign
- benign reactive hyperplasia - Malignant
- primary lymphoma/leukemia
- secondary malignancy
- metastatic carcinoma
- metastatic sarcoma
- metastatic melanoma
What are the patterns in a benign reactive lymph node
- cortex follicular hyperplasia
- mainly B cells - sinus histiocytosis
- dilated sinuses, containing histiocytes, lymphocytes, antigen presenting cells - paracortical hyperplasia
- mainly T cells - granulomatous reaction
- TB, sarcoidosis, Crohn’s disease, foreign body reaction, syphilis, connective tissue disorder
What is follicular hyperplasia
Activation of B cells within germinal centre formation in cortex of node
- non specific reaction
- infection/immune stimulation
Causes of benign reactive node
- infection
- bacterial
- viral
- parasitic
- protozoal - granulomas
- TB
- sarcoidosis
- Crohn’s disease
- histoplasmosis
- bruncellosis
- infectious mononucleosis
- syphilis
- cat scratch disease - deposits
- amyloidosis - immune reaction
- rheumatoid arthritis
- systemic lupus erythematosus - storage disorders
- Gaucher’s disease
What is
a) acute reactive lymphadenitis
b) chronic reactive lymphadenitis
a) lymphadenopathy usually secondary to bacterial or viral infection in the area drained by the lymph node
- clinically enlarged and tender
b) response to chronic antigen exposure
- e.g. collagen vascular disease
Histological features of actue reactive lymphadenitis
- preservation of the architecture
- follicular hyperplasia
- neutrophilic infiltrate and abscess formation
Example of collagen vascular disease/Immune-mediated disease
- RA
- generalised lymphadenopathy
- follicular hyperplasia - Sjoren’s syndrome
- follicular hyperplasia
- increased risk of lymphoma - SLE
- cervical lymphadenopathy
- follicular hyperplasia
Types of granuloma
- Caseating
- TB
- fungal infections - histoplasmosis, cryptococcus, blastomycosis, cat scratch disease
- rheumatoid nodules
- Wegener’s granulatosis - Non-caseating
- sarcoid
- beryllium
- hypersensitivity
- drug reactions
- leprosy
- Crohn’s disease
- chronic granulomatous disease
- Hodgkins lymphoma
