Haematological Malignancies Flashcards
What is the morphology of a normal lymph node
It is kidney shaped
It receives lymph via afferent vessels and then filtered lymph leaves via two efferent vessels
The capsule of the lymph node is a dense connective tissue stroma
The cortex of the lymph node - outer cortex layer is named the B cell layer
Paracortex is where T cells are activated in response to antigens
The medulla is the innermost layer of the lymph node and contains large blood vessels, sinuses and medullary cords.
What do the medullary cords in the lymph node do
The cord contains antibody secreting plasma cells, B cells and macrophages
What is the function of the lymph node
It is to filter the interstitial fluid that is collected from soft tissues and eventually returning it to the vasculature system
The lymph percolates through the lymph node and is scrutinized by the macrophages and lymphocytes ready to mount an immune response
What are various non-malignant causes of lymph node enlargement
- Suppurative lymphadenitis
- Tuberculosis
- Sarcoidosis
- Toxoplasmosis
- Cat scratch disease
- Kikuchi disease
What is suppurative lymphadenitis
A condition where a lymph node become inflamed and filled with pus due to an acute bacterial infection
- Bacterial infections can involve regional lymph nodes and lead to acute lymphadenitis that may become suppurative
-Infections are often caused by S. aureus or Streptococcus pyogenes: these bacteria enter through wounds, skin infections or mucosal surfaces, then travel to nearby lymph nodes via lymphatic vessels.
What are the clinical features of suppurative lymphadenitis
Painful, swollen lymph node (neck/armpit or groin)
Redness/warmth over the affected area
Fever or systemic symptoms if the infection spreads
May progress to fluctuant mass
What is the histology/pathology of suppurative lymphadenitis
- Enlarged lymph nodes filled with neutrophils (the immune cells that fight bacteria)
- Formation of abscesses (localized pus collection)
- Necrosis of lymph node tissue in severe cases
- May show edema, vascular congestion, and sinus histiocytosis
What is Tuberculosis
This is a chronic infectious disease caused by the bacterium Mycobacterium Tuberculosis. It primarily affects the lungs but can also spread to other organs.
What is the cause of TB
Caused by Mycobacterium tuberculosis, a slow-growing, acid-fact bacillus
Spread by airborne droplets from coughing, sneezing, or talking from an infected person
What is the pathogenesis of TB
1) Inhalation of TB bacteria: it reaches the lungs
2) Macrophages try to ingest the bacteria but it cannot be killed effectively
3) Bacteria start to multiple inside the macrophages - this leads to a cell-mediated immune response
4) Immune system walls off the infection and forms a granuloma:
- Central caseous necrosis
- Surrounding immune cells like epithelioid cells, Langhans giant cells and lymphocytes.
5) The bacteria may become latent or years and reactivate later
What are the symptoms of TB
- Night sweats
- Weight loss
- Fever
- Persistent cough sometimes with blood
- Fatigue
- Chest pain
What is the typical progression of TB
- Starts in the lungs
- Lymphadenitis is the most frequent extrapulmonary site occurring usually in the cervical region
- In people without HIV, TB tends to be localised - it only affects one area
- In people with HIV, it is a multifocal disease as their immune system is weaker, so TB tends to be more widespread: it can affect multiple organs at the same time.
How is TB diagnosed
- Chest X-ray
- Tuberculin skin test (Mantoux)
- Sputum test for AFB
- PCR for rapid identification
What is the histology of necrotizing granuloma
- Caseous necrosis (central necrosis)
- Surrounding epithelioid histiocytes
- Multinucleated giant cells
- Lymphocytes at the periphery
- Fibrosis (in chronic cases)
What does the central necrosis consist of
- The center of the granuloma is dead tissue - it looks amorphous and pink
- This happens when immune cells try to kill the invader but the tissue dies in the process
What does the surrounding epithelioid cells consist of
Around the necrotic center, there would be epithelioid histiocytes (specialised macrophages)
These are large, pink-staining cells with elongated nuclei - they try to contain the infection
What do multinucleated giant cells consist of
- Formed when multiple macrophages duse together
- Langhans-type giant cells are often seen (nuclei arranged in a horseshoe pattern around the edge of the cell)
What do the lymphocytes at the periphery consist of
- T cells surround the granuloma to help regulate the immune response
- These are small, dark purple staining cells
What happens in the fibrosis
If the granuloma has been present for a long time, the body may lay down fibrous tissue around it to wall it off
What is the Ziehl-Neelsen Stain
This is the stain that is used for Acid-Fast Bacilli like Mycobacterium tuberculosis
M. tuberculosis have thick, waxy walls made of mycolic acids
These cell walls make it hard for regular stains to enter but once the dye gets in, it doesn’t come out even when washed with acid - the bacteria will appear red
What is Sarcoidosis
Sarcoidosis is a multisystem inflammatory disease characterised by the formation of non-caseating granulomas (organised clusters of immune cells) in various organs - most commonly lungs, lymph nodes, skin, and eyes.
What causes Sarcoidosis
The exact cause is unknown but it is thought to be due to an abnormal immune response to an unknown environmental trigger in genetically susceptible individuals
It is not infectious or cancerous
What is the histology of Sarcoidosis
- Non-caseating granulomas (meaning there’s no central necrosis like in TB)
- Composed of epithelioid histiocytes (activated macrophages), multinucleated giant cells, and T lymphocytes
- May contain Schaumann bodies or asteroid bodies (microscopic inclusions)
What are the clinical features of Sarcoidosis
- Low-grade features
- Fatigue
- Weight loss
