pleura and mediastinal pathology

Question 1

Pleural effusion

Answer 1

Accumulation of fluid (>15 ml) in the pleural space secondary to: increase in hydrostatic pressure–> transudate (CHF,lymphatic blockage via tumor)

Decreased osmotic pressure –> transudate (nephrotic syndrome, cirrhosis, malnutrition)

Increased vascular permeability-> exudate (pneumonia)

Question 2

Transudate vs Exudate

Answer 2

transudate: extracascular fluid that has a low level of protein, low specific gravity, and low cellularity
Due to increased hydrostatic pressure or decreased oncotic pressure

Exudate: extravascular fluid that has a high level of protein, high level of protein high specific gravity and increased cellularity, due to vascular permeability

Question 3

Pleural effusion clinical presentation:

Answer 3

Dyspnea, pleuritc pain and cough, enlarged hemithorax, dullness on percussion, decreased or absent breath sounds, compression of the lung( atelectasis leading to repiratory distress

Management: CXR, thoracocentesis, analysis of pleral fluid, chemisty, culture, cytology, pleural biopsy (percutaneous, open), treatment of underlying cause)

Question 4

Common causes of pleural effusion

Answer 4

Infections: bacterial pneumonia, viral disease, TB

Pulmonary embolism, malignant neoplasm, trauma

Systemic conditions: CHF, cirrhosis, Nephrotic syndrome collagen vascular diseases

Question 5

pleural effusions types

Answer 5

Inflammatory pleural effusions: serofibrinous suppurative(empyema), hemmorrhagic

Non - inflammatory pleural effusions: hydrothrox, hemothroax, chylothorax

Question 6

Inflammatory pleural effusions

Answer 6

serous, fibrinous, and serofibrinous: inflammatory condtions such aspneumonia, TB lung infarcts and abcesses

Purulent exydate: empyema: localized accumulation of pus due to organsims,

Hemorrhagic pleurits: coagulopathies, rickettsial disease, malignant neoplasms

Question 7

Empyema (pyothorax)

Answer 7

Purulent pleural effusions complicating lung infections (Pneumococci, staphilococci, and streptococci)

Suppurative pleuritis
Pleural surface is coated by shaggy thick fibrin lung infections (pneumococci, staphilocci and streptococci) with green purulent exudate

Organization produces adhesions and loculation circumscribing the pus and limiting lung expansion

Surgical decotrication is treatment of choice

Question 8

Non inflammatory effusions

Answer 8

Hydrothorax: clear serous fluid (cardiac failure, pulmonary congestion and edema, cirrohosis, uremia, renal failure

Hemothrorax: hemorrhagic fluid: ruptured aortic aneurysm, trauma

Chylothorax: milky fluid (thoracic ducuts trauma, or lymphatics occlusion secondary to malignancy)

Question 9

Pneumothorax

Answer 9

Presence of air or gas within the pleural cavity
Spontaneous- traumatic- therapeutic
Mostcommonly associated with emphysema, asthma and tb
Spontaneous idiopathic pneumothorax: encountered in young individuals secondary to rupture of spall apical blebs the trachia is deviated to the ipsilatereal side, usually subsides spontaneously
Tension pneumothorax: when the defects acts as a flap that permits entrance of air during inspiration but doesnt allow escape of air during expiration

Question 10

Pneumothorax mechanism

Answer 10

Perforation of the visceral pleura and entry of air from the lung

Penetration of air from the chest wall, diaphragm, mediastinum or esophagus, gas forming organisms in empymea

Question 11

clinical symptoms of pneumothorax

Answer 11

Chest pain, dyspnea, absent breath sounds on ausultation

Tympanitic percussion (hyper resonance)
Contralateral deviation of the trachea on CXR, compression and collapse of lung parenchyma with atelactasis, marked respiratory distress

Question 12

Spontaneous pneumothorax

Answer 12

may be idiopathic (unknown cause), secondary to rupture of pleural bleb or bulla, bronchopleural fistula, bullous emphysema

Question 13

Tension pneumothorax

Answer 13

Due to penetrating trauma to the lungs, produces increased pleural cavity pressure with compression and atelectasis, flap like pleural defect acts like a valve allowing air in but not out

Sudden onset of respiratory distress (medical emergency)

Trachea deviated to contralateral side of pneumothorax

Question 14

Pleural neoplasms

Answer 14

benign: solitary fibrous tumor (pleural fibroma)
Malignant: metastases from other organs, malignant mesothelioma

Question 15

Solitary fibrous tumor

Answer 15

Soft tissue (mesenchymal) tumor
Polypoid, well circumscribed, pedunculated, 

Composed of fibroblasts with abundant collagenized stroma, microscopic appearance: spindle cells

Benign tumor, cured by simple excision

Mostly asymptomatic and discovered incidentally on chest X rays

Associated with hypoglycemia and clubbing of the fingers

Question 16

malignant mesothelioma

Answer 16

neoplastic proliferation of mesothelial cells ligning serosal surface, most common in adults over 50

Asbestos exposiore, radiotion, chronic inflammation, viral infections, idiopathic

Asbestos related mesothelioma: epidemiologic studies (coastal areas), lifetime risk for devloping mesothelioma is up to 10% in pts with a history of heavy exposure, long latency period (20-40 yrs), occupational exposure millworkers, roofing material textiles, insulation, shipyard workers

Insidious slow growing neoplasms, recurrent pleural effusions, chest pain and dyspnea, 20% pts have fibrosis, fatal malignancy

Question 17

malignant mesothelioma pathology

Answer 17

Tumor characteristically spread along mesothelial surface, composed of bland appearing cuboidal cells (well-differentiated neoplasm)
Very difficult for pathologist to distinguish mesothelioma from metastatic carcinoma to the pleura

Can also involve other serosal surfaces

Question 18

metastatic tumors

Answer 18

Metastatic tumors are more common than primary malignancies in the pleura
Lung is the most frequent source of metasteses to the pleura, other tumors include breast and avarian cancer, pancreas, kidney

Spread is by blood, lymphatics or direct extension
Mets are often multiple and bilatera

Question 19

inflammation of the mediastinum

Answer 19

Acute mediastinits (complication of conditions affecting neighboring organs, esophageal perforation, perforation of lung abcess, sternal osteomyelitis)

Granulomatous mediastinatis (chronic disorder secondary to fungal or mycobacterial infection)- Histoplasmosis, tuberculosis, crytococcosism atypical mycobacteria, aspergillosis

Idiopathic scelrosing mediastinitis (unknown etiology)

Congenital cysts: Usually unilocular, children aged 5- 15 years, lined by simple cuboidal epithelium, may be filled with serous fluid

Question 20

myasthenia gravis

Answer 20

May be associated with thymic lesions- thymic hyperplasia, thymoma, thymic carcinoma

Auto- anti bodies form to acetylcholine receptors in neuromuscular junction

Autosenstization to AChR is initiated in the thymus due to defective confrontation of Ach-secreting thymic myoid cells with T cells

Symptoms: weakness, fatigability, ptosis, diplopia`

Question 21

Thymic hyperplasia

Answer 21

Thymic lymphoid follicular hyperplasia: associated with myasthenia gravis and other autoimmune disorder

Question 22

Tumors of the mediastinum

Answer 22

Posterior: Neruogenic tumors (Schwannoma, neurofibroma, ganglioneruoma, neuroblastoma)

Middle: (metastatic tumors, pericardial cyst, bronchogenic cyst, lymphomas)

Anterior-Superior: Metastatic tumors, thymoma thymuc CA, lymphomas, germ cell tumors, sarcomas, congenital thymic cysts

Question 23

Thymoma

Answer 23

Neoplastic proliferation of thymic epithelial cells
usually contains lots of immature T cells (non neoplastic) frequently associated with MG and other paraneoplastic syndromes

May be composed of spindle cells or round epithelioid cells, slow growing tumor that may recur but rarely mets

Symptoms: asymptomatic in 30%, cough, dyspnea, chest pain, SVC syndrome, paraneoplastic syndromes, myasthenia gravis, pure red cell aplasia, hypogammaglobinemia, agranulocytosis, white blood cell aplasia, polymyositis sle, pemphigus vulgaris disseminated herpes, spindle cells A and round cells B and AB

Clincal behavior: depends on the status of the capsule, encapsulated tumors are cured by complete surgical exxcision, invasice tumors tend to recur repeatedly and may eventually metastasize, recurrent tumors may progress to thymic carcinoma

Question 24

thymic carcinoma

Answer 24

Resemble other types of carcinoma occuring in other organs (squamous small cell, adenocarcinoma), most are sqaumous cell carcinomas, diagnosis of exclusion (there are no specific features that permit definit histologic diagnisis)