🏗️ Normal Anatomy & Defense
Conducting vs. Respiratory Portions
Nasal organ / Pharynx / Larynx→
Trachea→
L/R Bronchi→
Bronchioles (<1mm)→
Terminal bronchioles (<0.5mm)
Respiratory bronchioles→
Alveolar ducts→
Alveolar sacs→
Pulmonary alveoli
The pulmonary acinus is the basic functional unit (respiratory bronchiole → alveolus).
Tracheal Wall Layers (inner → outer)
Epithelium
Lamina propria
Submucosa
Cartilage
Adventitia
Epithelium type: Pseudostratified ciliated columnar epithelium (goblet cells + basal cells + ciliated cells)
Defense Mechanisms
- 🦠 Rhinothrix (nasal hair baffle)
- 🌊 Cilia-mucus transport system
- 💉 Local immunity — IgA in secretions, alexin, lysozyme
- 🦠 Alveolar macrophages
🦠 Section 1 — Pneumonia
Section 1
By Distribution
- Lobar pneumonia
- Lobular (broncho)pneumonia
- Interstitial pneumonia
🫁 Lobar Pneumonia
Basics
- Etiology: Streptococcus pneumoniae
- Affected: 30–50 yr, previously healthy
- Type: Diffuse exudative fibrinous inflammation in alveoli
- Spread: Via Kohn's pores → entire lobe
Clinical Signs
- Sudden chill, fever
- "Rusty" sputum (hemosiderin)
- Pleuritic chest pain
- Friction rub
- Dyspnea + cough
📌 Four Classic Stages (~7–10 days)
🧠 Mnemonic
Can Red Grapes Resolve? → Congestion → Red hepatization → Gray hepatization → Resolution
① Congestion (Days 1–2)
- Dark red, boggy lobe
- Frothy red fluid
- Vascular congestion
- Proteinaceous fluid + neutrophils + bacteria in alveoli
② Red Hepatization (Days 3–4)
- Red, firm, liver-like lobe
- Alveoli packed with fibrin, RBCs, neutrophils, bacteria
- Vascular congestion persists
- Fibrinous pleural exudate possible
③ Gray Hepatization (Days 5–6)
- Dry, gray, firm, liver-like
- Vascular congestion diminished
- Alveoli: fibrin + lots of neutrophils, fewer bacteria
- Capillaries compressed
④ Resolution (>1 week)
- Enzymatic degradation of exudate
- Macrophage clearance
- Normal structure restored
- Favorable outcome
⚠️ Complications
Pulmonary carnification
Empyema
Abscess
Septicemia / Pyemia
Infectious shock
Carnification = fibrin not absorbed → organized into brown flesh-like fibrous tissue (due to ↓neutrophil proteinase or excess fibrin)
🫁 Lobular (Broncho)Pneumonia
Basics
- Etiology: Staphylococci, streptococci, pneumococci (pyogenic bacteria)
- Affected: Children, elderly, debilitated patients
- Type: Acute suppurative inflammation
- Also called: Bronchopneumonia
Morphology
- Patchy distribution, multifocal, bilateral, basal
- Centred around inflamed small bronchi/bronchioles
- Neutrophil-rich exudate fills bronchi + alveoli
- Compensative emphysema in adjacent alveoli
- Pleural involvement less common
⚠️ Complications
Respiratory failure
Heart failure
Abscess
Pyemia
Empyema
Bronchiectasis
📊 Lobar vs. Lobular — Quick Comparison
| Feature | Lobar Pneumonia | Lobular / Bronchopneumonia |
|---|
| Organism | Pneumococci | Pyogenic bacteria |
| Age | 30–50 yr, healthy | Children, elderly, debilitated |
| Pattern | Entire lobe; 4 classic stages | Patchy; multifocal; bilateral; basal |
| Inflammation | Fibrinous / serous | Suppurative (neutrophil-rich) |
| Complications | Carnification, septicemia, shock | Bronchiectasis, heart/respiratory failure |
| Onset | Sudden, chills, rusty sputum | Fever, cough, purulent sputum |
🦠 Viral Pneumonia
Pathogens
- Influenza virus
- Respiratory syncytial virus (RSV)
- Adenovirus
- Parainfluenza virus
- Cytomegalovirus (CMV)
- Measles virus
Key Features
- 🫁 Interstitial pneumonia — alveolar walls widened, edematous, mononuclear cell infiltration
- 💧 Hyaline membrane — less sputum, dyspnea
- 🔴 Viral inclusion bodies (diagnostic!)
- 👁️ Multinuclear giant cells (alveolar epithelium)
🔍 Viral Inclusion Bodies (Diagnostic)
- Round/oval, erythrocyte-like in size
- Mostly eosinophilic with halos
- CMV → in nuclei
- Measles → in cytoplasm
- Formed by aggregation of complete virus particles or unassembled virus subunits
💨 Section 2 — COPD & Pulmonary Emphysema
Section 2
ℹ️
COPD = group of conditions with chronic/recurrent airflow obstruction. Includes: chronic bronchitis, emphysema, bronchiectasis, asthma.
Pulmonary Emphysema
Definition: Abnormal permanent enlargement of airspaces distal to terminal bronchioles + destruction of walls without obvious fibrosis.
Pathogenesis — Two Key Imbalances
⚖️ Protease – Antiprotease
Smoking / α1-AT deficiency
→
↑ Elastase
→
Elastic damage
→
Emphysema
⚖️ Oxidant – Antioxidant
Smoking → oxidative stress → inactivates α1-antitrypsin → functional deficiency
Both imbalances are additive
📌 Four Types of Emphysema
| Type | Location Affected | Key Association |
|---|
| Centriacinar | Respiratory bronchioles dilate | Cigarette smoking (most common) |
| Panacinar | Entire acinus uniformly enlarged | α1-antitrypsin deficiency |
| Distal acinar | Near pleura and lobular septa | Spontaneous pneumothorax (young adults) |
| Irregular | Irregular, around scars | Healed inflammatory disease; often asymptomatic |
Gross & Microscopic Findings
Gross
- Enlarged lungs with blunt margins
- Pale/gray-white, soft, no elasticity
- Honeycomb-like appearance
Microscopy
- Large irregular airspaces
- Thinned alveolar walls
- Adjacent alveoli coalesce → large airspaces
- Septal capillaries compressed & bloodless
Clinical Features
- Insidious dyspnea
- Barrel-shaped chest (enlarged lungs)
- Pneumothorax risk
- Secondary pulmonary hypertension (hypoxia + loss of capillary surface)
- Cor pulmonale (right heart failure)
⛏️ Section 3 — Silicosis
Section 3
⚠️
Most important pneumoconiosis. Caused by inhalation of SiO₂ <5μm for 5–10 years. Results in chronic nodular dense pulmonary fibrosis + TB risk.
Sources of Exposure
- Mining (gold, tin, copper, coal)
- Quarrying
- Sandblasting
- Metal grinding
- Ceramics manufacture
Pathogenesis
SiO₂ inhaled → macrophages engulf
↓
Hydrated silica → lysosome damage
↓
Macrophage necrosis → SiO₂ released
↓
Re-engulfed (cycle repeats)
↓
Cytokine release → Fibrosis
Morphology Progression
| Stage | Finding |
|---|
| Early | Cellular silicotic nodules (small, upper lobes) |
| Intermediate | Fibrous nodules with hyaline change |
| Advanced | Collagenous nodules; hyalinized whorls of collagen; diffuse interstitial fibrosis |
⚠️ Complications
Pulmonary TB (most important!)
Cor pulmonale (right heart failure)
Emphysema + pneumothorax
❤️ Section 4 — Chronic Cor Pulmonale
Section 4
💡
Definition: Right ventricular hypertrophy + dilation (± failure) secondary to pulmonary hypertension caused by lung or pulmonary vascular disorders.
Pathogenesis
COPD
→
↓ BV → Hypoxemia
→
Pulmonary artery spasm
→
↑ Pulmonary resistance
→
↑ Pulmonary artery pressure
→
Right heart hypertrophy/dilation
Pathological Changes
Lung Changes
- COPD features present
- Arteriole walls thicken (collagen, elastic fiber in media & intima)
- Muscularization of arterioles
- ↓ Capillaries
Heart Changes
- Right ventricular wall hypertrophy
- Thickened trabeculae + papillary muscles
- Hypertrophic myocardial cells (microscopy)
👃 Section 5a — Nasopharyngeal Carcinoma (NPC)
Tumor
Epidemiology
- Common in Southern China (Guangdong, Zhujiang), Indonesia, Malaysia, N. Africa
- Male : Female = 2:1
- Peak age: 40–50 years
- Originates from nasopharyngeal epithelium
Etiology
- 🦠 EBV infection (primary cause)
- ↑ IgA against EBV in patients
- EBV DNA/RNA in tumor cells
- EBV in precursor lesions
- 🧪 Nitrosamines (salted fish — dimethylnitrosamine)
- 🧬 Genetic factors
Common Location
Nasopharyngeal roof > lateral wall > pharyngeal recess
Histological Types
| Type | Details |
|---|
| Keratinizing SqCC | Well differentiated; keratin pearls; intercellular bridges |
| Non-keratinizing (differentiated) | Poorly differentiated; no keratinization |
| Undifferentiated ★ most common | Vesicular nucleus cell carcinoma ("lymphoepithelioma"); large nuclei, 1–2 nucleoli; lymphocytes intermixed; radiosensitive, better prognosis |
| Adenocarcinoma | Less common |
Spread & Metastasis
1️⃣ Direct Extension
- Upward → base of skull → cranial nerves II–VI damage
- Lateral → auditory tube → middle ear; eye sockets
- Forward → nasal cavity
- Backward → cervical vertebrae
2️⃣ Lymphatic (early)
Upper deep cervical LN enlargement = first signal
3️⃣ Hematogenous
Liver, lung, bone
Prognosis
- Radiosensitive
- 5-year survival: ~50% (advanced); 80% for T1N0M0
- Early detection: IgA against EBV viral capsid antigen (VCA) in serum
🫁 Section 5b — Carcinoma of the Lung
Tumor
📊
#1 cancer cause of death in industrialized countries. Most common in men 40–70 yr (M:F = 2:1). Incidence in women increasing due to smoking.
Etiology
🚬 Cigarette Smoking (main cause)
- 20× increased risk in heavy smokers
- Carcinogens: polycyclic hydrocarbons, aromatic amines, heavy metals (nickel)
- Progression: squamous metaplasia → dysplasia → CIS → invasive
Other Causes
- Industrial: asbestos (best-known), uranium, nickel, chromate
- Air pollution: ozone, N oxides, S oxides
- Molecular: c-myc, K-ras, p53, Rb, p16
Gross Types by Position
| Type | Origin | Notes |
|---|
| Central (hilar) | Major bronchi (1st–3rd order) | 75% cases; related to smoking; usually SqCC |
| Peripheral | Small bronchi / bronchioles / alveoli | Single/multiple nodules; more common in women |
| Diffuse | 2–5% of lung cancer | Miliary nodules; can mimic pneumonia or TB |
Histological Classification
NSCLC — 70–75%
| Type | Key Features | Association |
|---|
| Squamous Cell Ca |
Central; preceded by metaplasia/dysplasia; necrosis + cavitation common |
Smoking; males |
| Adenocarcinoma ★ most common overall |
Peripheral; grows rapidly; early/wide hematogenous spread; subtypes: acinar, papillary, micropapillary, lepidic, etc. |
Women, non-smokers, <45 yr |
| Large Cell Ca |
Undifferentiated; large nuclei + prominent nucleoli; no SqCC or gland features; likely undifferentiated SqCC/AdCa |
Poor prognosis |
⚡ SCLC — Small Cell Carcinoma (20–25%)
- Most malignant lung cancer
- Central/hilar origin; strongly linked to smoking
- Oat cells — oval/short spindle, dark nuclei, scant cytoplasm
- Derived from neuroendocrine cells → neurosecretory granules
- Positive for chromogranin, synaptophysin
- Secretes peptide hormones → paraneoplastic syndromes
- Almost always metastasized at diagnosis
- Treatment: chemotherapy ± radiation (not surgery)
📊 NSCLC vs. SCLC Comparison
| Feature | NSCLC | SCLC |
|---|
| Cytoplasm | Abundant | Scant |
| Nuclei | Pleomorphic | Small, dark |
| Chromogranin | Negative | Positive |
| Synaptophysin | Negative | Positive |
| Treatment | Surgery (preferred) | Chemotherapy |
| Prognosis | Better | Worse |
| Molecular changes | P16, cyclinD1, K-ras | P53, RB mutations |
Patterns of Spread
Direct Extension
- Airway obstruction (central type)
- Pericardial/pleural effusion
- Superior vena cava syndrome (SVC compression)
- Apical: brachial plexus + cervical sympathetic → Horner's syndrome (enophthalmos, ptosis, miosis, anhydrosis)
Lymphatic & Hematogenous
- Hilar → paratracheal → cervical → Virchow's node
- Hematogenous: liver, bone, adrenal, brain
- Metastases may appear before primary is symptomatic
Prognosis & Diagnosis
📉
Overall 5-year survival ≈ 9%. Surgical resection (NSCLC, localized): 30–40% 5-yr survival. Early detection is critical!
Diagnostic Methods
Sputum cytology
Fibreoptic bronchoscope + biopsy
X-ray / CT / MRI
Fine-needle aspiration biopsy
Pleural effusion cytology
⚠️ High suspicion in adults >40 yr with long smoking history + cough/dyspnea/chest pain/position-related cough.
✅ Chapter Quick-Review Summary
| Topic | Key Buzzwords |
|---|
| Lobar Pneumonia | Pneumococcus, fibrinous, 4 stages (Congestion→Red→Gray→Resolution), rusty sputum, carnification |
| Lobular Pneumonia | Pyogenic bacteria, suppurative, patchy/basal, children/elderly, bronchiectasis |
| Viral Pneumonia | Interstitial, viral inclusion bodies (CMV nuclear, Measles cytoplasm), hyaline membrane |
| Emphysema | Permanent airspace enlargement, protease-antiprotease imbalance, barrel chest, 4 types, smoking/α1-AT |
| Silicosis | SiO₂, macrophage cycling, collagenous nodules, hyaline whorls, TB complication |
| Cor Pulmonale | RV hypertrophy, pulmonary HTN, secondary to COPD/lung disease |
| NPC | EBV, Southern China, undifferentiated most common, lymphoepithelioma, radiosensitive, IgA-VCA screening |
| Lung Cancer | Smoking, SqCC (central/male), AdCa (peripheral/women/most common), SCLC (oat cell/neuroendocrine/chemo), 9% 5-yr survival |