Cystic-Cavitary Lung Lesions

General Definitions

  • Cavity (Pathologic Definition): gas-filled space within a zone of pulmonary consolidation or within a mass or nodule, produced by the expulsion of a necrotic part of the lesion via the bronchial tree
  • Cavity (Radiographic Definition): lucency within a zone of pulmonary consolidation, a mass, or a nodule
    • Hence, a lucent area within the lung that may or may not contain a fluid level and that is surrounded by a wall, usually of varied thickness

Definitions Based on Wall Thickness

  • Cyst: < or = 4 mm wall thickness at thickest point
  • Cavity: >4 mm wall thickness at thickest point (or with surrounding mass or infiltrate)


Mechanisms of Cavity Formation

  • Suppurative Lung Necrosis
    • Example: pyogenic lung asbcess
  • Caseous Lung Necrosis
    • Example: tuberculosis
  • Ischemic Lung Necrosis
    • Example: pulmonary infarction
  • Cystic Dilation of Lung Structures
    • Example: Pneumocystis jirovecii pneumonia and ball valve obstruction
  • Displacement of Lung Tissue by Cystic Structure
    • Example: Echinococcosis
  • Treatment-Related Necrosis
    • Example: malignancy
  • Internal Cyst Formation
    • Example: malignancy
  • internal Desquamation of Tumor Cells with Subsequent Liquefaction
    • Example: malignancy

Probability of Malignancy

  • Wall Thickness: wall thickness is positively correlated with the probability of malignancy (although there is considerable overlap, so it is not a good discriminatory tool)
    • Wall thickness <4 mm: 92% of lesions are benign
    • Wall thickness >15 mm: 95% of lesions are malignant
  • Presence of Air-Fluid Level: presence of air-fluid level is not associated with the probability of malignancy

Etiology of Cystic Lesion

Congenital Cystic Lung Lesions

  • Bronchogenic Cyst (see Bronchogenic Cyst, [[Bronchogenic Cyst]]): approximately 33% are located within the lung parenchyma (usually within the lower lobes), although most are within the mediastinum
    • May contain air, fluid (with homogeneous appearance), or both
    • May become secondarily infected or impinge on other structures
  • Congenital Adenomatoid Malformation (see Congenital Adenomatoid Malformation, [[Congenital Adenomatoid Malformation]]): presents as cystic or solid lung mass, restricted to one part of the lung


  • Echinococcosis (see Echinococcosis, [[Echinococcosis]]): cystic lesions are more commonly multiple (than single), with wall thickness ranging in size from 2 mm-1 cm


  • Metastases to Lungs: rarely present with cystic lung lesions

Pneumatocele (see Pneumatocele, [[Pneumatocele]])

General Comments

  • Definition: cystic airspace within the lung which characteristically increases in size over days-weeks (probably due to ball-valve air trapping mechanism), but eventually resolves

Infection-Associated Pneumatocele

  • Adenovirus (see Adenovirus, [[Adenovirus]])
  • Coccidioidomycosis (see Coccidioidomycosis, [[Coccidioidomycosis]])
  • Escherichia Coli (see Escherichia Coli, [[Escherichia Coli]]): uncommon etiology
  • Haemophilus Influenzae (see Haemophilus Influenzae, [[Haemophilus Influenzae]]): uncommon etiology
  • Klebsiella Pneumoniae (see Klebsiella Pneumoniae, [[Klebsiella Pneumoniae]]): uncommon etiology
  • Necrotizing Pneumonia (see Necrotizing Pneumonia, [[Necrotizing Pneumonia]])
  • Pneumocystis Jirovecii (see Pneumocystis Jirovecii, [[Pneumocystis Jirovecii]]): cystic lesions are usually seen in HIV-associated cases, are more common in upper lobes, and range in size from 1-5 cm
  • Pseudomonas Aeruginosa (see Pseudomonas Aeruginosa, [[Pseudomonas Aeruginosa]]])
  • Serratia Marcescens (see Serratia Marcescens, [[Serratia Marcescens]])
  • Staphylococcus Aureus (see Staphylococcus Aureus, [[Staphylococcus Aureus]])
    • Pneumatoceles occur mainly in childhood cases
    • Case reports associated with Staph Aureus endocarditis with septic embolization
  • Streptococcus Pneumoniae (see Streptococcus Pneumoniae, [[Streptococcus Pneumoniae]]): uncommon etiology
  • Streptococcus Pyogenes (see Streptococcus Pyogenes, [[Streptococcus Pyogenes]]): uncommon etiology
  • Tuberculosis (see Tuberculosis, [[Tuberculosis]])

Toxin-Associated Pneumatocele

  • Hydrocarbon Aspiration Pneumonitis (see Hydrocarbons, [[Hydrocarbons]])

Traumatic Pneumatocele

  • Penetrating or Closed Chest Trauma
  • Ventilator-Associated Barotrauma (see Acute Lung Injury-ARDS, [[Acute Lung Injury-ARDS]])


  • Blebs (see Chronic Obstructive Pulmonary Disease, [[Chronic Obstructive Pulmonary Disease]]: defined as localized subpleural (or intrapleural) collection of air usually <1 cm in diameter
    • HRCT: blebs are usually located in the lung apex
  • Bullae (see Chronic Obstructive Pulmonary Disease, [[Chronic Obstructive Pulmonary Disease]]): defined as sharply demarcated air-containing space at least 1 cm in diameter, with smooth wall that is <1 mm thick
    • HRCT: bullae usually result from coalescense of emphysematous airspaces or from ball-valve airway obstruction
  • Ehlers-Danlos Syndrome (see Ehlers-Danlos Syndrome, [[Ehlers-Danlos Syndrome]])
  • Follicular Bronchiolitis (see Follicular Bronchiolitis, [[Follicular Bronchiolitis]])
    • HRCT:
  • Hyper IgE-Recurrent Infection Syndrome (Job’s Syndrome/Buckley-Job Syndrome) (see Hyper IgE-Recurrent Infection Syndrome, [[Hyper IgE-Recurrent Infection Syndrome]]
    • HRCT:
  • Langerhans Cell Histiocytosis (see Langerhans Cell Histiocytosis, [[Langerhans Cell Histiocytosis]]): serial HCRT suggests progression from nodules -> cavitating nodules -> cystic lesions
    • HRCT: upper zone cysts/honeycombing -> most cysts are <1 cm in diameter (however, large cysts may occur as disease progresses) with barely perceptible to few mm wall thickness
  • Lymphangioleiomyomatosis (LAM) (see Lymphangioleiomyomatosis, [[Lymphangioleiomyomatosis]])
    • HRCT: diffuse, thin-walled cysts (2-40 mm in diameter with walls 0.1-2 mm in thickness) -> usually, >10 cysts are present
  • Lymphocytic Interstitial Pneumonia (LIP) (see Lymphocytic Interstitial Pneumonia, [[Lymphocytic Interstitial Pneumonia]])
    • HRCT: ground-glass infiltrates and centrobular nodules, but may also have thin-walled cysts (in 66% of cases)
  • Subacute Hypersensitivity Pneumonitis (HP) (see Hypersensitivity Pneumonitis, [[Hypersensitivity Pneumonitis]])
    • HRCT: cysts (3-25 mm) are seen in 13% of patients with subacute HP, usually in association with ground-glass infiltrates
      • Cysts resemble those of lymphoid interstitial pneumonia (see Lymphocytic Interstitial Pneumonia, [[Lymphocytic Interstitial Pneumonia]]): like the cysts of lymphoid interstitial pneumonia, they are presumably caused by partial bronchiolar obstruction by the peribronchiolar lymphocytic infiltrates
  • Tuberous Sclerosis (see Tuberous Sclerosis, [[Tuberous Sclerosis]])
    • HRCT: diffuse thin-walled cysts -> usually <1 cm in diameter (may be as large as 3 cm in some cases), usually round/ovoid (may be polygonal in advanced disease), and more numerous/larger in females

Etiology of Cavitary Lesion (Cavitary Infiltrate/Nodule)


  • Actinomycosis (see Actinomycosis, [[Actinomycosis]])
  • Amebiasis (see Amebiasis, [[Amebiasis]])
  • Anaerobes (see Aspiration Pneumonia, [[Aspiration Pneumonia]]
  • Blastomycosis (see Blastomycosis, [[Blastomycosis]])
  • Chronic Pulmonary Aspergillosis (see Chronic Pulmonary Aspergillosis, [[Chronic Pulmonary Aspergillosis]])
  • Clostridium Perfringens (see Clostridium Perfringens, [[Clostridium Perfringens]]): associated with necrotizing, cavitary pneumonia and PE
  • Coccidioidomycosis (see Coccidioidomycosis, [[Coccidioidomycosis]])
  • Cryptococcosis (see Cryptococcosis, [[Cryptococcosis]]): cavitation is more common in patients receiving steroids (as in HIV-related cases on PCP therapy)
  • Cytomegalovirus (CMV) (see Cytomegalovirus, [[Cytomegalovirus]]): may cavitate in HIV-related cases
  • Echinococcosis (see Echinococcosis, [[Echinococcosis]]): cystic lesions are more commonly multiple (than single), with wall thickness ranging in size from 2 mm-1 cm
  • Gram-Negative Bacteria
  • Histoplasmosis (see Histoplasmosis, [[Histoplasmosis]])
  • Invasive Pulmonary Aspergillosis (see Invasive Pulmonary Aspergillosis, [[Invasive Pulmonary Aspergillosis]])
  • Klebsiella Pneumoniae (see Klebsiella Pneumoniae, [[Klebsiella Pneumoniae]])
    • Epidemiology: common etiology of cavitation (due to extensive pgenic lung necrosis)
  • Lung Abscess (see Lung Abscess, [[Lung Abscess]])
  • Melioidosis (see Burkholderia Pseudomallei, [[Burkholderia Pseudomallei]])
  • Mucormycosis (see Mucormycosis, [[Mucormycosis]])
  • Mycobacterium Abscessus (see Mycobacterium Abscessus, [[Mycobacterium Abscessus]])
  • Mycobacterium Avium-Intracellulare (MAI) (see Mycobacterium Avium-Intracellulare, [[Mycobacterium Avium-Intracellulare]])
  • Mycobacterium Kansasii (see Mycobacterium Kansasii, [[Mycobacterium Kansasii]])
  • Mycobacterium Xenopi (see Mycobacterium Xenopi, [[Mycobacterium Xenopi]])
  • Necrotizing Pneumonia (see Necrotizing Pneumonia], [[Necrotizing Pneumonia]])
  • Nocardiosis (see Nocardiosis, [[Nocardiosis]])
  • Paragonimiasis (see Paragonimiasis, [[Paragonimiasis]])
  • Pneumocystis Jirovecii (see Pneumocystis Jirovecii, [[Pneumocystis Jirovecii]])
  • Rhodococcus Equi (see Rhodococcus Equi, [[Rhodococcus Equi]])
  • Septic Embolism (see Septic Embolism, [[Septic Embolism]])
    • Diagnosis
      • Usually multiple well-defined pulmonary nodules in varying states of cavitation
      • Usually 1-3 cm in diameter
      • May be accompanied by subpleural wedge-shaped infiltrates
  • Sporotrichosis (see Sporotrichosis, [[Sporotrichosis]])
  • Staphylococcus Aureus (see Staphylococcus Aureus, [[Staphylococcus Aureus]])
    • Epidemiology: common cause of necrotizing pneumonia and cavitation
  • Streptococcus (see Streptococcus, [[Streptococcus]])
  • Tuberculosis (see Tuberculosis, [[Tuberculosis]]):
    • Epidemiology
      • Cavitation is common in post-primary TB predominantly involving the upper lobes
      • Tuberculosis is the most common infection to result in cavitation: due to the extent of caseous necrosis
    • Diagnosis: cavity walls may be smooth or irregular
    • Clinical: tendency to form cavities enhances propagation of tuberculosis, since cavities contain large numbers of organisms which can be aerosolized and transmitted to other hosts


Primary Lung Neoplasm

  • Lung Cancer (see Lung Cancer, [[Lung Cancer]]): cavitation occurs in 10-15% of lung cancers
    • Epidemiology
      • Cavitation occurs on 7-11% of lung cancers (by CXR) and 22% of cases (by CT scan)
      • Cavitation is more common in squamous cell histology
      • Presence of cavitation portends a worse prognosis

Metastases to Lung

  • General Comments: only 4% of mets to lung are cavitary by CXR
  • Breast Cancer (see Breast Cancer, [[Breast Cancer]])- Bronchioloalveolar Cell Carcinoma (see Bronchioloalveolar Cell Carcinoma, [[Bronchioloalveolar Cell Carcinoma]])
  • Colon Cancer (see Colon Cancer, [[Colon Cancer]])
  • Kaposi Sarcoma (see Kaposi Sarcoma, [[Kaposi Sarcoma]]): cavitation is particularly common in HIV-associated cases
  • Leiomyosarcoma (see Leiomyosarcoma, [[Leiomyosarcoma]])
  • Lymphoma (see Lymphoma, [[Lymphoma]]): cavitation is particularly common in HIV-associated cases
  • Sarcomas
  • Squamous Cell Carcinoma of Upper Aerodigestive Tract
  • Urothelial Cell Carcinoma (Transitional Cell Carcinoma) (see Urothelial Cell Carcinoma, [[Urothelial Cell Carcinoma]])

Pulmonary Vasculitis

  • Churg-Strauss Syndrome (see Churg-Strauss Syndrome, [[Churg-Strauss Syndrome]]): infiltrates rarely cavitate
  • Rheumatoid Nodules (see Rheumatoid Arthritis, [[Rheumatoid Arthritis]])
    • Epidemiology: usually associated with rheumatoid skin nodules
    • Diagnosis
      • Usually pleural or subpleural
      • Associated with interlobular septae
      • Upper lobe predominance
      • More commonly multiple than single
  • Wegener’s Granulomatosis (see Wegener’s Granulomatosis, [[Wegeners Granulomatosis]])
    • Epidemiology: 10% of cases have cavitary nodules
    • Diagnosis: more commonly multiple than single


  • Acute Pulmonary Embolism With Pulmonary Infarction (see Acute Pulmonary Embolism, [[Acute Pulmonary Embolism]]): infarction occurs in <15% of PE cases -> only about 5% of infarctions cavitate
  • Amiodarone (see Amiodarone, [[Amiodarone]]): may uncommonly cause a hyperdense infiltrate/mass which may cavitate
  • Amyloidosis (see Amyloidosis, [[Amyloidosis]]): rare etiology of cavitation
  • Ankylosing Spondylitis (see Ankylosing Spondylitis, [[Ankylosing Spondylitis]])
    • Diagnosis: apical fibrobullous disease
  • Bronchiectasis (Localized) (see Bronchiectasis, [[Bronchiectasis]])
  • Congenital Adenomatoid Malformation (see Congenital Adenomatoid Malformation, [[Congenital Adenomatoid Malformation]])
  • Crack Cocaine (see Cocaine, [[Cocaine]])
  • Cryptogenic Organizing Pneumonia (COP) (see Cryptogenic Organizing Pneumonia, [[Cryptogenic Organizing Pneumonia]]): solitary focal COP pattern (nodule) which may cavitate
  • Langerhans Cell Histiocytosis (see Langerhans Cell Histiocytosis, [[Langerhans Cell Histiocytosis]]): serial HCRT suggests progression from nodules -> cavitating nodules -> cystic lesions
    • HRCT: upper zone cysts/honeycombing -> most cysts are <1 cm in diameter (however, large cysts may occur as disease progresses) with barely perceptible to few mm wall thickness
  • Lymphomatoid Granulomatosis (see Lymphomatoid Granulomatosis, [[Lymphomatoid Granulomatosis]]): frequently presents with cavitation
  • Progressive Massive Fibrosis/Pneumoconiosis (see Progressive Massive Fibrosis, [[Progressive Massive Fibrosis]]): irregularly-shaped fibrotic masses typically in upper lobes, which may cavitate (due to ischemic necrosis)
  • Pulmonary Sequestration (see Pulmonary Sequestration, [[Pulmonary Sequestration]])
  • Sarcoidosis (see Sarcoidosis, [[Sarcoidosis]]): aka Necrotizing Sarcoid Angiitis and Granulomatosis
    • Epidemiology: cavitation occurs in 6.8% of cases

Etiology of Apical Fibrobullous Disease


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