SPECIAL SELECTED TOPICS- RESPIRATORY SYSTEM DISORDERS-SSTRSDO-QAA 026

1. What are the main characteristics of bronchogenic carcinomas?

Bronchogenic carcinoma is the most common primary malignant tumor of the lung and a leading cause of cancer-related death worldwide. Most cases are strongly associated with cigarette smoking. The tumor usually arises from the bronchial epithelium after progressive dysplastic and malignant transformation.

Bronchogenic carcinomas are aggressive tumors with early local invasion and distant metastasis. Patients commonly present with cough, hemoptysis, chest pain, dyspnea, or recurrent pneumonia. Some tumors produce paraneoplastic syndromes due to ectopic hormone secretion. Histologically, they are classified into several major subtypes.

Early diagnosis is often difficult because symptoms appear late. Prognosis depends mainly on histological type and clinical stage.

2. Which etiologic agents have been known to promote lung cancers?

Cigarette smoking is the single most important etiological factor responsible for lung cancer. Passive smoking also increases the risk. Occupational exposure to asbestos, arsenic, chromium, nickel, beryllium, and uranium contributes significantly. Radon gas exposure is an important cause, especially in underground miners and poorly ventilated buildings.

Air pollution and diesel exhaust increase the incidence of lung cancer. Previous pulmonary fibrosis and chronic lung disease predispose to malignant transformation. Ionizing radiation is another recognized carcinogenic factor.

Genetic susceptibility influences individual risk. Smoking combined with asbestos exposure produces a synergistic increase in lung cancer risk.

Avoidance of tobacco remains the most effective preventive measure.

3. List the main histologic types of bronchogenic carcinomas.

Bronchogenic carcinomas are classified into four major histological types. Squamous cell carcinoma arises from bronchial epithelium and often shows keratinization. Adenocarcinoma originates from gland-forming epithelial cells and is the most common type overall.

Small cell carcinoma is a highly malignant neuroendocrine tumor with early metastasis. Large cell carcinoma is an undifferentiated malignant epithelial tumor lacking features of the other types.

Additional less common variants include adenosquamous carcinoma and sarcomatoid carcinoma. Histological classification guides treatment decisions.

Molecular testing is especially important in adenocarcinoma. Accurate pathological diagnosis is essential for prognosis and therapy.

 

4. What is the most common histologic type of lung cancer?

Adenocarcinoma is currently the most common histologic type of lung cancer worldwide. It occurs in both smokers and non-smokers but is particularly common among non-smokers and women. The tumor usually arises in the peripheral parts of the lung.

Histologically, it forms glands or produces mucin. Many tumors harbor mutations involving EGFR, ALK, KRAS, or other molecular pathways. Molecular testing is essential because targeted therapy improves survival in selected patients.

Adenocarcinoma may invade the pleura and metastasize early. Clinical presentation includes cough, dyspnea, chest pain, or incidental radiological detection.

Prognosis depends primarily on tumor stage at diagnosis.

5. How are lung cancers divided according to their response to chemotherapy?

Lung cancers are broadly divided into small cell lung carcinoma (SCLC) and non-small cell lung carcinoma (NSCLC) according to their biological behavior and response to treatment. Small cell carcinoma responds well initially to chemotherapy and radiotherapy because of its high mitotic activity.

However, recurrence is common, and long-term survival remains poor. Non-small cell carcinomas include squamous cell carcinoma, adenocarcinoma, and large cell carcinoma. These tumors respond less effectively to chemotherapy than small cell carcinoma.

Surgical resection is the preferred treatment for localized NSCLC. Targeted therapy and immunotherapy have significantly improved outcomes in selected patients.

Accurate classification is essential for choosing appropriate treatment.

6. Which types of carcinomas are most closely related to smoking?

Squamous cell carcinoma and small cell carcinoma show the strongest association with cigarette smoking. Nearly all patients with small cell carcinoma have a significant smoking history.

Squamous cell carcinoma develops through squamous metaplasia and dysplasia induced by tobacco smoke. Large cell carcinoma also has a strong association with smoking. Adenocarcinoma is associated with smoking but also commonly occurs in non-smokers.

Tobacco smoke contains numerous carcinogens that produce genetic mutations in bronchial epithelial cells. The risk increases with the duration and intensity of smoking.

Smoking cessation substantially reduces future cancer risk. Tobacco control remains the most effective preventive strategy.

7. In which parts of the lung do most bronchogenic carcinomas arise?

The site of origin varies according to the histological subtype of bronchogenic carcinoma. Squamous cell carcinoma usually arises centrally in the main, lobar, or segmental bronchi. Small cell carcinoma also commonly originates in the central bronchi.

Adenocarcinoma most frequently develops in the peripheral lung parenchyma, often near the pleura. Large cell carcinoma may arise either centrally or peripherally. Peripheral tumors may invade the pleura and chest wall.

Central tumors commonly produce bronchial obstruction, atelectasis, and recurrent pneumonia. Knowledge of tumor location assists radiological diagnosis and biopsy planning.

Tumor site also influences clinical presentation and surgical management.

8. Describe the most common pathways of lung cancer spread.

Lung carcinoma spreads by direct invasion, lymphatic dissemination, hematogenous metastasis, and transcoelomic extension. Direct invasion involves the pleura, chest wall, mediastinum, diaphragm, or pericardium. Lymphatic spread first involves hilar and mediastinal lymph nodes.

Hematogenous spread commonly affects the brain, liver, adrenal glands, bones, and opposite lung. Pleural involvement may produce malignant pleural effusion.

Tumor cells may invade major blood vessels and bronchi. Small cell carcinoma metastasizes particularly early and extensively. Distant metastases are often present at the time of diagnosis. The extent of metastatic spread is a major determinant of prognosis.

9. What are the main pathologic features of squamous cell carcinoma of the lung?

Squamous cell carcinoma usually arises centrally from the major bronchi and is strongly associated with cigarette smoking. It develops through a sequence of squamous metaplasia, dysplasia, carcinoma in situ, and invasive carcinoma.

Grossly, the tumor forms a firm gray-white mass that may obstruct the bronchial lumen. Central necrosis frequently produces cavitation. Microscopically, malignant squamous cells show keratinization and intercellular bridges.

Tumor differentiation varies from well differentiated to poorly differentiated forms. Local invasion commonly involves adjacent bronchi and mediastinal structures.

Hypercalcemia may occur due to ectopic production of parathyroid hormone-related peptide (PTHrP). Surgical resection offers the best outcome in localized disease.

10. What are the main pathologic features of adenocarcinoma of the lung?

Adenocarcinoma is the most common primary lung cancer and usually arises in the peripheral lung parenchyma. It originates from glandular epithelial cells or type II pneumocytes. Grossly, it appears as a firm gray-white peripheral mass, often associated with pleural retraction.

Microscopically, the tumor forms glands or produces intracellular or extracellular mucin. Several histological patterns, including acinar, papillary, micropapillary, solid, and lepidic, may be present.

Molecular abnormalities involving EGFR, ALK, ROS1, and KRAS are common. The tumor invades pleura, lymphatics, and blood vessels in advanced stages. Regional lymph node and distant metastases may occur early.

Histological subtype and molecular profile guide targeted therapy and prognosis.

11. What are the main morphologic characteristics of bronchioloalveolar carcinoma?

Bronchioloalveolar carcinoma is now classified as adenocarcinoma in situ or lepidic-predominant adenocarcinoma. The tumor usually arises in the peripheral lung and may appear as a solitary nodule or diffuse pneumonic-type consolidation.

Microscopically, neoplastic cells grow along intact alveolar septa in a lepidic pattern without destroying the underlying lung architecture in early lesions. Mucin-producing and non-mucinous variants are recognized.

Stromal, vascular, and pleural invasion are absent in adenocarcinoma in situ but appear in invasive forms. Multiple bilateral lesions may occur. The surrounding alveolar framework is initially preserved.

Prognosis is excellent for non-invasive lesions after complete surgical excision. Invasive lesions behave like conventional adenocarcinoma.

12. Discuss the clinical symptoms caused by bronchioloalveolar carcinoma.

Patients commonly present with persistent cough and gradually progressive dyspnea. Copious watery sputum (bronchorrhea) is a characteristic feature in mucinous tumors. Hemoptysis may occur but is usually mild.

Chest pain is uncommon unless pleural invasion develops. Fever may lead to confusion with pneumonia. Weight loss and fatigue occur in advanced disease. Chest radiographs may show a solitary peripheral nodule or diffuse infiltrative shadows resembling pneumonia.

The tumor often responds poorly to antibiotics because it mimics infection. Early diagnosis depends on imaging, bronchoscopy, biopsy, and histopathological examination.

Prognosis is favorable in localized adenocarcinoma in situ but less favorable in diffuse invasive disease.

13. What are the main pathologic features of small cell carcinoma of the lung?

Small cell carcinoma is a highly malignant neuroendocrine tumor strongly associated with cigarette smoking. It usually arises centrally near the main bronchi. Grossly, it forms a soft gray-white infiltrative mass with extensive necrosis.

Microscopically, the tumor consists of small round or spindle-shaped cells with scant cytoplasm, finely granular chromatin, and numerous mitotic figures. Nuclear molding is a characteristic feature.

The tumor shows extensive vascular invasion and early metastasis. Neuroendocrine markers such as chromogranin, synaptophysin, and CD56 are typically positive. Ectopic hormone production commonly causes paraneoplastic syndromes.

sBecause dissemination occurs early, surgery is rarely useful, and chemotherapy with radiotherapy is the primary treatment.

14. Discuss the origin of large cell carcinoma of the lung.

Large cell carcinoma is an undifferentiated malignant epithelial tumor that lacks the histological features of squamous cell carcinoma, adenocarcinoma, or small cell carcinoma. It probably arises from primitive bronchial epithelial stem cells capable of multidirectional differentiation.

The tumor may occur in either central or peripheral parts of the lung. Grossly, it forms a large soft mass with areas of hemorrhage and necrosis. Microscopically, it contains large pleomorphic cells with abundant cytoplasm, prominent nucleoli, and frequent mitoses. Gland formation and keratinization are absent.

SThe tumor grows rapidly and metastasizes early. Prognosis is generally poor because most patients present with advanced disease. Treatment follows the principles used for non-small cell lung carcinoma.

15. How do lung carcinomas present clinically?

Lung carcinoma often remains asymptomatic during its early stages. Persistent cough is the most common presenting symptom. Hemoptysis, chest pain, dyspnea, and recurrent pneumonia occur because of airway obstruction or local invasion.

Constitutional symptoms include weight loss, anorexia, fatigue, and fever. Hoarseness results from recurrent laryngeal nerve involvement. Superior vena cava obstruction causes facial swelling and venous congestion. Pancoast tumors produce shoulder pain and Horner syndrome due to brachial plexus involvement.

Many patients present with symptoms caused by distant metastases involving the brain, bones, liver, or adrenal glands. Early detection through imaging significantly improves survival.

16. Describe the importance of histologic type and clinical stage in the prognosis and therapy of patients with lung cancer.

Histological classification determines the biological behavior and treatment strategy of lung cancer. Small cell carcinoma is highly aggressive and is treated mainly with chemotherapy and radiotherapy because surgery is rarely beneficial.

Non-small cell carcinomas are managed primarily by surgical resection when localized. Clinical staging using the TNM system is the most important prognostic factor. Early-stage tumors have significantly better survival than advanced metastatic disease.

Molecular testing identifies patients suitable for targeted therapies such as EGFR or ALK inhibitors. Immunotherapy has improved outcomes in selected advanced tumors.

Histological type predicts response to specific treatments. Accurate staging and pathological diagnosis are essential for individualized management and prognosis.

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17. What are the most frequent paraneoplastic syndromes in patients with lung cancer?

Paraneoplastic syndromes result from ectopic hormone production or immune-mediated mechanisms rather than direct tumor invasion. Small cell carcinoma commonly produces ACTH, causing Cushing syndrome, and ADH, causing syndrome of inappropriate antidiuretic hormone secretion (SIADH).

Squamous cell carcinoma frequently secretes parathyroid hormone-related peptide (PTHrP), resulting in hypercalcemia. Neurological syndromes include Lambert-Eaton myasthenic syndrome and peripheral neuropathy.

Hypertrophic pulmonary osteoarthropathy and digital clubbing are well-recognized manifestations. Hypercoagulability may lead to migratory thrombophlebitis. Dermatomyositis and polymyositis occur occasionally.

Recognition of paraneoplastic syndromes may facilitate early diagnosis of occult lung cancer. Successful treatment of the primary tumor often improves these manifestations.

18. List the main histologic subtypes of neuroendocrine tumors of the lungs.

Pulmonary neuroendocrine tumors are classified into four major histological subtypes based on differentiation and biological behavior. Typical carcinoid tumor is a low-grade neuroendocrine neoplasm with an excellent prognosis. 

Atypical carcinoid tumor is an intermediate-grade tumor with increased mitotic activity and focal necrosis. Large cell neuroendocrine carcinoma is a high-grade malignant tumor with aggressive clinical behavior. Small cell carcinoma is the most aggressive neuroendocrine carcinoma and metastasizes early.

All neuroendocrine tumors express markers such as chromogranin, synaptophysin, and CD56. Prognosis worsens progressively from typical carcinoid to small cell carcinoma. Histological grading guides treatment and predicts survival.

19. What are the main clinical and pathologic characteristics of bronchial carcinoids?

Bronchial carcinoids are well-differentiated neuroendocrine tumors arising from Kulchitsky cells of the bronchial mucosa. They account for a small proportion of primary lung tumors and usually occur in younger patients.

Most tumors arise centrally within the major bronchi and produce cough, wheezing, recurrent pneumonia, or hemoptysis because of bronchial obstruction. Grossly, they appear as well-circumscribed, highly vascular, polypoid masses projecting into the bronchial lumen. Microscopically, uniform neuroendocrine cells are arranged in nests, trabeculae, or rosettes.

Typical carcinoids have few mitoses and no necrosis, whereas atypical carcinoids show increased mitotic activity and focal necrosis. Carcinoid syndrome is uncommon because vasoactive substances are usually metabolized in the lungs. Surgical excision is the treatment of choice.

The prognosis is excellent for typical carcinoids and intermediate for atypical carcinoids.

20. List the usual features of metastatic tumors in the lungs.

 

The lungs are one of the most common sites of metastatic spread because they receive the entire cardiac output through the pulmonary circulation. Metastases commonly arise from cancers of the breast, colon, kidney, thyroid, prostate, liver, and malignant melanoma.

Grossly, metastatic tumors usually appear as multiple, well-circumscribed, rounded nodules of varying sizes scattered throughout both lungs. Some tumors produce diffuse lymphangitic spread or pleural involvement.

Histologically, the metastatic tumor resembles the primary malignancy. Patients may be asymptomatic or present with cough, dyspnea, chest pain, or hemoptysis. Chest CT is highly sensitive for detecting pulmonary metastases.

Treatment depends on the primary tumor, extent of metastasis, and patient's clinical condition. Pulmonary metastases generally indicate advanced-stage malignancy and carry a guarded prognosis.

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 DR.C.GANESAN M.D

PROFESSOR OF MEDICINE

     

SPECIAL SELECTED TOPICS- RESPIRATORY SYSTEM DISORDERS-SSTRSDO-QAA 025

1. What is the pathogenesis of pleural effusion?

Pleural effusion is the abnormal accumulation of fluid within the pleural cavity due to imbalance between pleural fluid formation and absorption. Increased hydrostatic pressure, as in congestive heart failure, produces transudative effusions.

Reduced plasma oncotic pressure due to nephrotic syndrome, liver cirrhosis, or malnutrition also causes transudates. Increased vascular permeability from infections, malignancy, pulmonary embolism, or inflammatory diseases results in exudative effusions.

Obstruction of lymphatic drainage by tumors impairs fluid removal. Hemothorax and chylothorax represent specialized forms of pleural effusion. Progressive fluid accumulation compresses the lung and causes dyspnea.

Thoracentesis and pleural fluid analysis help determine the underlying cause. Treatment is directed at correcting the primary disease.

2. Which forms of pleuritis do you know?

Pleuritis is inflammation of the pleura resulting from infections, autoimmune diseases, malignancy, or pulmonary disorders. Acute fibrinous pleuritis is characterized by deposition of fibrin on the pleural surfaces and often produces pleuritic chest pain with a pleural friction rub.

Serous pleuritis results in accumulation of clear inflammatory fluid. Suppurative pleuritis (empyema) contains purulent exudate due to bacterial infection.

Hemorrhagic pleuritis occurs in tuberculosis, malignancy, or trauma. Chronic fibrous pleuritis produces pleural thickening and adhesions. Tuberculous pleuritis is an important granulomatous form.

Chronic inflammation may lead to pleural fibrosis and restriction of lung expansion. Identification of the underlying cause guides treatment.

3. What are the main types of non-inflammatory pleural effusions?

Non-inflammatory pleural effusions are mainly transudative and result from systemic disorders rather than pleural inflammation. Hydrothorax is a transudative pleural effusion caused by congestive heart failure, nephrotic syndrome, or liver cirrhosis.

Hemothorax is the accumulation of blood in the pleural cavity following trauma, surgery, or rupture of blood vessels. Chylothorax results from leakage of lymph due to thoracic duct injury or obstruction by tumors. Urinothorax occurs rarely after urinary tract injury. These effusions usually lack significant inflammatory cells.

Large effusions compress the underlying lung and impair ventilation. Pleural fluid analysis distinguishes transudates from exudates. Management depends on treatment of the underlying condition.

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 DR.C.GANESAN M.D

PROFESSOR OF MEDICINE

 

SPECIAL SELECTED TOPICS- RESPIRATORY SYSTEM DISORDERS-SSTRSDO-QAA 024

1. What are the most frequent pleural tumors?

Pleural tumors may be primary or secondary. Metastatic involvement of the pleura from lung, breast, ovarian, or gastrointestinal cancers is far more common than primary pleural tumors. Malignant mesothelioma is the most important primary malignant pleural tumor and is strongly associated with asbestos exposure.

Solitary fibrous tumor is the most common benign primary pleural neoplasm. Pleural metastases often produce malignant pleural effusion. Patients commonly present with chest pain, dyspnea, cough, and pleural effusion. Imaging studies demonstrate pleural thickening or nodular masses.

Histopathology and immunohistochemistry establish the diagnosis. Prognosis depends on the tumor type and extent of disease.

2. Which etiologic agents are associated with malignant mesothelioma?

Malignant mesothelioma is strongly associated with occupational exposure to asbestos fibers, particularly amphibole asbestos such as crocidolite. The disease typically develops after a long latent period of 20–50 years following exposure.

Workers in shipbuilding, construction, insulation, and asbestos manufacturing are at highest risk. Unlike bronchogenic carcinoma, smoking does not significantly increase the risk of mesothelioma. Chronic asbestos exposure causes repeated mesothelial injury, inflammation, and genetic mutations.

Germline or somatic alterations involving the BAP1 tumor suppressor gene have been identified in many patients. The tumor most commonly involves the pleura but may also affect the peritoneum.

Strict occupational safety measures have reduced its incidence in many countries. Prognosis remains poor despite modern treatment.

3. What are the morphologic characteristics of malignant mesothelioma?

Malignant mesothelioma usually presents as diffuse nodular thickening of the pleura that progressively encases the lung like a rigid shell. The pleural surface becomes gray-white, firm, and irregular. The tumor invades the chest wall, diaphragm, pericardium, and adjacent lung tissue.

Microscopically, three major patterns are recognized: epithelioid, sarcomatoid, and biphasic (mixed). The epithelioid type forms tubules, papillae, or sheets of polygonal cells. The sarcomatoid type consists of spindle-shaped malignant cells resembling fibrosarcoma.

Immunohistochemistry helps distinguish mesothelioma from metastatic adenocarcinoma. Extensive pleural fibrosis and recurrent hemorrhagic effusions are common. Local invasion predominates, although distant metastases may occur in advanced disease.

4. What is the clinical course of disease in patients with malignant mesothelioma?

Malignant mesothelioma has an insidious onset and an aggressive clinical course. Patients usually present with progressive dyspnea, persistent chest pain, dry cough, fatigue, and weight loss. Recurrent pleural effusions are common and often hemorrhagic. As the tumor enlarges, it encases the lung, causing severe restriction of lung expansion and respiratory impairment. Local invasion into the chest wall produces persistent pain.

Diagnosis is established by imaging, thoracoscopy, biopsy, and immunohistochemical studies. Most patients present with advanced disease because early symptoms are nonspecific.

Treatment includes surgery in selected patients, chemotherapy, immunotherapy, and palliative care. Despite advances in management, the overall prognosis remains poor, with a median survival of approximately 12–18 months after diagnosis.      

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DR.C.GANESAN M.D

PROFESSOR OF MEDICINE

 

SPECIAL SELECTED TOPICS- RESPIRATORY SYSTEM DISORDERS-SSTRSDO-QAA 023

1. Describe the content of a typical empyema.

 

Empyema is the accumulation of pus within the pleural cavity, usually resulting from bacterial pneumonia, lung abscess, thoracic surgery, or chest trauma. The pleural cavity contains thick yellow-green purulent exudate composed of numerous neutrophils, necrotic cellular debris, fibrin, bacteria, and protein-rich fluid.

The pleural surfaces become inflamed, roughened, and coated with fibrin. As healing occurs, fibroblasts organize the fibrin, leading to pleural adhesions and fibrosis. Untreated empyema may become loculated and difficult to drain. Severe cases may progress to sepsis or bronchopleural fistula.

Patients present with fever, pleuritic chest pain, cough, and dyspnea. Prompt drainage combined with appropriate antibiotics is essential for successful treatment.

2. Describe the main types of pneumothorax.

Pneumothorax is the presence of air within the pleural cavity, resulting in partial or complete collapse of the lung. Spontaneous pneumothorax occurs without trauma and is classified as primary or secondary.

Primary spontaneous pneumothorax commonly results from rupture of subpleural blebs in otherwise healthy young adults. Secondary spontaneous pneumothorax develops in patients with underlying lung diseases such as COPD, tuberculosis, cystic fibrosis, or interstitial lung disease.

Traumatic pneumothorax follows penetrating or blunt chest injury or medical procedures. Tension pneumothorax is a life-threatening emergency in which air enters the pleural cavity but cannot escape, causing progressive mediastinal shift and cardiovascular compromise.

Patients present with sudden chest pain, dyspnea, and reduced breath sounds. Immediate decompression is required in tension pneumothorax.

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 DR.C.GANESAN M.D

PROFESSOR OF MEDICINE

 

SPECIAL SELECTED TOPICS- RESPIRATORY SYSTEM DISORDERS-SSTRSDO-QAA 022

List the most common therapy-related pulmonary complications.

Therapy-related pulmonary complications occur following medications, radiation, chemotherapy, oxygen therapy, or bone marrow transplantation. Drug-induced pneumonitis is commonly caused by bleomycin, amiodarone, methotrexate, and nitrofurantoin. Radiation therapy may produce acute radiation pneumonitis followed by pulmonary fibrosis.

Oxygen toxicity causes diffuse alveolar damage after prolonged administration of high oxygen concentrations. Chemotherapy may predispose to opportunistic pulmonary infections due to immunosuppression.

Pulmonary edema may occur after massive blood transfusion or fluid overload. Bronchiolitis obliterans may develop after lung or stem cell transplantation. Pulmonary embolism is another important treatment-related complication.

Early recognition and withdrawal of the offending agent improve outcomes. Careful monitoring minimizes therapy-associated lung injury.

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DR.C.GANESAN M.D

PROFESSOR OF MEDICINE

 

SPECIAL SELECTED TOPICS- RESPIRATORY SYSTEM DISORDERS-SSTRSDO-QAA 021 

Which diseases belong to pulmonary hemorrhage syndromes?

Pulmonary hemorrhage syndromes are characterized by bleeding into the alveolar spaces causing hemoptysis and anemia. Goodpasture syndrome is an autoimmune disease caused by antibodies against the glomerular and alveolar basement membranes. Granulomatosis with polyangiitis (Wegener granulomatosis) commonly produces pulmonary hemorrhage associated with systemic vasculitis. 

Microscopic polyangiitis is another important cause of diffuse alveolar hemorrhage. Systemic lupus erythematosus may also produce pulmonary hemorrhage. Idiopathic pulmonary hemosiderosis causes recurrent alveolar bleeding without an identifiable systemic disease. Histologically, alveoli contain numerous hemosiderin-laden macrophages.

Patients present with hemoptysis, dyspnea, anemia, and diffuse pulmonary infiltrates. Early diagnosis and immunosuppressive therapy improve clinical outcomes.

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DR.C.GANESAN M.D

PROFESSOR OF MEDICINE

 

SPECIAL SELECTED TOPICS- RESPIRATORY SYSTEM DISORDERS-SSTRSDO-QAA 020

1. Describe the difference between usual interstitial pneumonia (UIP) and desquamative interstitial pneumonia (DIP).

interstitial pneumonia

  

desquamative interstitial pneumonia

Usual interstitial pneumonia (UIP) is the histologic pattern of idiopathic pulmonary fibrosis and is characterized by patchy interstitial fibrosis with marked temporal heterogeneity.

Normal lung alternates with areas of active fibroblast proliferation and dense fibrosis. Honeycomb lung is a prominent feature of advanced UIP. The prognosis is poor because fibrosis progresses relentlessly.

Desquamative interstitial pneumonia (DIP) is strongly associated with cigarette smoking. It is characterized by diffuse accumulation of macrophages within alveolar spaces rather than true desquamation of epithelial cells. Interstitial fibrosis is mild and relatively uniform.

DIP responds well to smoking cessation and corticosteroid therapy. The prognosis of DIP is considerably better than that of UIP.

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2. Define hypersensitivity pneumonitis.

Hypersensitivity pneumonitis, also called extrinsic allergic alveolitis, is an immunologically mediated inflammatory disease caused by repeated inhalation of organic antigens.

Common antigens include moldy hay, bird proteins, fungi, and contaminated humidifiers. Both type III immune complex and type IV delayed hypersensitivity reactions contribute to the disease. Inflammation primarily affects the alveoli and interstitium. Patients present with fever, cough, dyspnea, and malaise several hours after antigen exposure.

Chronic exposure leads to interstitial fibrosis and restrictive lung disease. Histology shows interstitial inflammation with poorly formed non-caseating granulomas. Avoidance of the offending antigen is the cornerstone of treatment. Corticosteroids are useful in severe or persistent cases.

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 DR.C.GANESAN M.D

PROFESSOR OF MEDICINE