21. Benign Lymphoid Proliferations

Question 1

List the lymphoid organs

Answer 1

1. lymph nodes
2. spleen
3. thymus
4. bronchial associated lymphoid tissue (BALT)
5. gastrointestinal associated lymphoid tissue (GALT)
6. Waldeyer ring

Question 2

Examples of primary lymphoid tissues

Answer 2

1. T cells
   - cell mediated immunity
   - matured in thymus
2. B cells
   - humoral immunity
   - matured in bone marrow
3. Null cells
   - not B or T cell marker responsive
4. NK cells
   - may react with T cells

Question 3

What is lymphopenia

Answer 3

abnormally low levels of lymphocytes

Question 4

Causes of lymphopenia

Answer 4

1. advanced HIV infection
2. congenital immune deficiency syndrome
3. steroid
4. chemotherapeutic drugs
5. autoimmune diseases

Question 5

What is lymphocytosis

Answer 5

excessive level of lymphocytes

Question 6

Causes of lymphocytosis

Answer 6

1. viral infection (most often)
   - infectious mononucleosis
2. bacterial infections (rare)
   - whooping cough
   - TB
   - brucellosis

Question 7

Type of lymphocytes in blood

Answer 7

1. T lymphocyte
2. B lymphocyte
3. Null cells
4. NK cells

Question 8

How do we recognise lymphocytes as either T or B or null

Answer 8

immunohistochemistry or flow cytometry

Question 9

Types of WBC neoplastic disorder

Answer 9

1. leukemia
   - cancer of bone marrow, blood, blast cells
   - acute/chronic and myeloid/lymphoid
   - if myeloid/lymphoid cells become malignant, it is known as ‘blasts’
2. lymphomas
   - lymph nodes, tumour
   - Hodgkins, non-Hodgkins (myeloma)
3. premalignant conditions
   - myeloproliferative syndrome
   - myelodysplastic syndrome

Question 10

Basic lymphocyte markers

Answer 10

1. CD45 stains most lymphocytes
2. T-lymphocyte - CD20, CD79
3. B-lymphocyte - CD3, CD2, CD4, CD5, CD8

Question 11

Explain T-cell cytotoxicity

Answer 11

1. cytotoxic T-cell
   - in infected cell, antigen associates with class I MHC molecule
   - T cell recognises the combination
2. T helper cell
   - in antigen presenting cell, antigen associates with class II MHC molecule
   - helper T cell recognises the combination
   - activate B cells

Question 12

Explain B-cell immunity

Answer 12

1. antigen recognition
2. activation of B lymphocytes
3. Proliferation
4. 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

Question 13

Types of mononuclear phagocytic cells

Answer 13

1. monocytes
   - differentiate into macrophages
2. histiocytes
   - phagocytosis and cytokine production
3. macrophage
   - histiocytes with more phagocytic function
4. multinucleated giant cell
5. dendritic cell
   - antigen presenting cell to T cell
6. langerhan cell
   - antigen presenting cell

Question 14

What are the clinical signs of lymphoid tissue proliferation

Answer 14

• lymphadenopathy
• splenomegaly
• hepatomegaly
• thymic enlargement
• marrow expansion
• masses in naropharynx, GIT

Question 15

Clinical features of lymphoid tissue proliferation

Answer 15

1. Malignant
   - single, firm, painless large node
2. Benign
   - soft, tender node

Question 16

Causes of an enlarged node

Answer 16

1. Benign
   - benign reactive hyperplasia
2. Malignant
   - primary lymphoma/leukemia
   - secondary malignancy
   - metastatic carcinoma
   - metastatic sarcoma
   - metastatic melanoma

Question 17

What are the patterns in a benign reactive lymph node

Answer 17

1. cortex follicular hyperplasia
   - mainly B cells
2. sinus histiocytosis
   - dilated sinuses, containing histiocytes, lymphocytes, antigen presenting cells
3. paracortical hyperplasia
   - mainly T cells
4. granulomatous reaction
   - TB, sarcoidosis, Crohn’s disease, foreign body reaction, syphilis, connective tissue disorder

Question 18

What is follicular hyperplasia

Answer 18

Activation of B cells within germinal centre formation in cortex of node

• non specific reaction
• infection/immune stimulation

Question 19

Causes of benign reactive node

Answer 19

1. infection
   - bacterial
   - viral
   - parasitic
   - protozoal
2. granulomas
   - TB
   - sarcoidosis
   - Crohn’s disease
   - histoplasmosis
   - bruncellosis
   - infectious mononucleosis
   - syphilis
   - cat scratch disease
3. deposits
   - amyloidosis
4. immune reaction
   - rheumatoid arthritis
   - systemic lupus erythematosus
5. storage disorders
   - Gaucher’s disease

Question 20

What is

a) acute reactive lymphadenitis
b) chronic reactive lymphadenitis

Answer 20

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

Question 21

Histological features of actue reactive lymphadenitis

Answer 21

• preservation of the architecture
• follicular hyperplasia
• neutrophilic infiltrate and abscess formation

Question 22

Example of collagen vascular disease/Immune-mediated disease

Answer 22

1. RA
   - generalised lymphadenopathy
   - follicular hyperplasia
2. Sjoren’s syndrome
   - follicular hyperplasia
   - increased risk of lymphoma
3. SLE
   - cervical lymphadenopathy
   - follicular hyperplasia

Question 23

Types of granuloma

Answer 23

1. Caseating
   - TB
   - fungal infections - histoplasmosis, cryptococcus, blastomycosis, cat scratch disease
   - rheumatoid nodules
   - Wegener’s granulatosis
2. Non-caseating
   - sarcoid
   - beryllium
   - hypersensitivity
   - drug reactions
   - leprosy
   - Crohn’s disease
   - chronic granulomatous disease
   - Hodgkins lymphoma