(CELL PATHOLOGY) lymph node pathology#

Question 1

what are the common causes of lymphadenopathy?

Answer 1

malignant → lymphoma, secondary mets (carcinoma, melanoma)

infective

• active infections → viral (e.g. EBV, influenza), bacterial
• chronic (HIV, TB)

multisystem/ inflammatory → sarcoidosis, SLE, RA

Question 2

what are the components and functions of the lymphatic system?

Answer 2

consists of:

• conducting system → lymphatic vessels (return interstitial fluid to circulation)
• lymphoid tissue → lymph nodes, spleen, MALT

functions:

• drains interstitial fluid into blood; fluid balance
• immune function - transports APCs, enables antigen presentation to naïve lymphocytes, initiates adaptive immune response
• fat absorption via intestinal lymphatics (lacteals)

Question 3

describe the structure, cells, and function of lymph nodes

Answer 3

structure

• bean-shaped encapsulated lymphoid organs; fibrous capsule with internal trabeculae
• divided into → CORTEX (B cell follicles; germinal centres), PARACORTEX (T-cells); MEDULLA (plasma cells, macrophages)
• afferent lymphatics in → efferent out (via hilum)

cells:

• B lymphocytes → antibody production
• T lymphocytes → cell-mediated immunity
• Dendritic cells (APCs) → antigen presentation
• Macrophages → phagocytosis

functions → filters lymph (traps pathogens & tumour cells), site of antigen presentation, activation + proliferation of lymphocytes → FORM ADAPTIVE IMMUNE RESPONSE

Question 4

how do causes differ between localised vs generalised lymphadenopathy?

Answer 4

localised → local infection (pharyngitis, dental abscess), TB, cat scratch disease, metastasis

generalised → viral (EBV, HIV, hepatitis), lymphoma, autoimmune (SLE/ RA), systemic infections (TB, syphilis)

Question 5

what is fine needle aspiration? what is it used for in lymphadenopathy?

Answer 5

a minimally invasive sampling technique using a thin needle to obtain cells

first-line test for lymphadenopathy to distinguish:

• reactive lymphoid cells → infection
• malignant lymphocytes → lymphoma (suggestive, not definitive)
• metastatic cells → carcinoma/melanoma

BUT can’t assess architecture → need excision biopsy to confirm lymphoma

Question 6

why is excision biopsy required in suspected lymphoma?

Answer 6

Needed to assess lymph node architecture

Required for definitive diagnosis + classification

FNA alone is insufficient

Question 7

what is lymphoma?

Answer 7

clonal malignant proliferation of lymphocytes arising from B cells, T cells, or NK cells

typically presents as solid lymph node masses

Question 8

what are the key differences between Hodgkin and Non-Hodgkin lymphoma?

Answer 8

Hodgkin lymphoma:

• Reed–Sternberg cells
• Predictable spread
• Good prognosis

Non-Hodgkin lymphoma (B/T cell):

• No RS cells
• Variable behaviour
• Often extranodal

Question 9

how are B-cell non-Hodgkin lymphomas classified by behaviour?

Answer 9

Indolent (low-grade) → slow, relapsing-remitting; not usually curable (most common is follicular lymphoma)

Aggressive (high-grade) → rapid progression; potentially curable with treatment (most common is DLBCL)

Question 10

how do lymphomas typically present?

Answer 10

Painless lymphadenopathy

± B symptoms (indicate systemic disease & worser prognosis)

May have mediastinal mass or splenomegaly

Question 11

what is the key pathological feature of Hodgkin lymphoma?

Answer 11

Reed–Sternberg cells (large, binucleate, “owl-eye”)

Derived from B lymphocytes

Question 12

what is sarcoidosis? features? key investigations & findings?

Answer 12

multisystem disease of unknown cause characterised by non-caseating granulomas with NO central necrosis

features:

• lymphadenopathy
• cough, dyspnoea
• uveitis
• erythema nodosum (tender red nodules on anterior shins)
• lupus pernio (blue-red/ purple nodules and plaques on nose, cheeks, ears, lips)

investigations:

• ACE levels ↑ (produced by epithelioid cells in granulomas)
• Hypercalcaemia (↑ vitamin D activation)
• ESR ↑
• CXR: bilateral hilar lymphadenopathy
• Biopsy: non-caseating granulomas

Question 13

what is a granuloma?

Answer 13

collection of activated macrophages (epithelioid cells) - forms to isolate infections, chronic inflammation, or foreign materials

Question 14

how do sarcoid granulomas differ from TB granulomas?

Answer 14

Sarcoidosis: non-caseating

TB: caseating (necrotic centre)

Question 15

what is the difference between acute and chronic sarcoidosis?

Answer 15

Acute → self-limiting (1–2 yrs), good prognosis

Chronic → progressive; pulmonary fibrosis → respiratory failure

Question 16

what clinical features suggest lymphoma rather than reactive lymphadenopathy?

Answer 16

Painless, rubbery nodes
Persistent/progressive
B symptoms
No obvious infection