Cavitating Mass
Jonathan H. Chung, MD
DIFFERENTIAL DIAGNOSIS
Common
Non-Small Cell Lung Cancer
Lung Metastases
Lung Abscess
Mycobacterial Pneumonia
Fungal Pneumonia
Pulmonary Septic Emboli
Pulmonary Laceration
Less Common
Progressive Massive Fibrosis
Wegener Granulomatosis
Lymphoma
Cystic Adenomatoid Malformation
Sequestration
Rare but Important
Hydatid (Echinococcal) Cyst
Amebic Lung Abscess
Lymphomatoid Granulomatosis
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
Cavity
Air-containing lesion, walls thicker than 4 mm, surrounding consolidation or mass
Cyst
Air-containing lesion, walls thinner than or equal to 4 mm, no surrounding consolidation or mass
Time course: Acute vs. chronic
Acute time course suggestive of infectious or inflammatory diseases
Thickness of cavity wall
Thickest portion of cavity thinner than 4 mm, highly suggestive of benign etiology
Thickest portion of cavity thicker than 15 mm, highly suggestive of malignant etiology
Nodularity of cavity wall
Smooth wall more often benign
Nodular wall more often malignant
Helpful Clues for Common Diagnoses
Non-Small Cell Lung Cancer
Most likely diagnosis for solitary nodule or opacity in smoker
Thick and nodular cavity wall, spiculated nodule or mass; most common in upper lobes
Very large lymph nodes (> 2 cm in short axis) suggestive of malignant etiology
Cavitation most common in squamous subtype
Lung Metastases
History of malignancy, particularly squamous cell carcinoma, transitional cell carcinoma, or sarcoma
Lower lung preponderance due to increased blood flow
Lung Abscess
Round, thick-walled cavity with smooth inner margins within consolidated lung
Often related to aspiration pneumonia; usually gravitationally dependent location
Slow resolution even with appropriate antimicrobial treatment
Mycobacterial Pneumonia
Usually post-primary tuberculosis
90% in apical segment of upper lobes or superior segment of lower lobes
Centrilobular or tree in bud nodules suggest endobronchial spread
Large airway stenosis
In contradistinction to primary tuberculosis, pleural effusions and lymphadenopathy uncommon
Fungal Pneumonia
Chronic endemic fungal pneumonia closely resembles fibrocavitary, post-primary tuberculosis
Upper lobe preponderance; often bilateral
Mediastinal or hilar lymphadenopathy unusual in chronic infection
Most often histoplasmosis; also chronic progressive pulmonary coccidioidomycosis or chronic blastomycosis
Persistent pulmonary coccidioidomycosis: Lower lung predominant, ill-defined nodules with cavitation
Pulmonary Septic Emboli
Frequently multiple, peripheral, basilar, and bilateral
Early cavitation
“Feeding vessel” sign: Vessel leads directly into nodule or mass
Loculated pleural effusion common
Pulmonary Laceration
History or other imaging findings suggestive of trauma
Pneumatocele or gas-fluid level
Helpful Clues for Less Common Diagnoses
Progressive Massive Fibrosis
Nodules from simple silicosis or coal worker’s pneumoconiosis coalesce into biapical mass-like consolidation
Lateral margin parallels chest wall, sharply defined
Medial inner edge less defined
Tendency to migrate centrally; peripheral lung becomes emphysematous
Wegener Granulomatosis
Bilateral, multiple nodules that can coalesce into masses; may cavitate
Associated with upper airway and renal abnormalities
Halo sign: Ground-glass opacities surrounding nodules/masses
Large airway stenosis: Most often subglottic trachea
Lymphoma
Cavitation unusual
Associated mediastinal lymphadenopathy with predilection for anterior mediastinum and thymus
Cystic Adenomatoid Malformation
Multicystic pulmonary lesion
May contain gas, fluid, or combination of gas and fluid
Normal interspersed lung parenchyma
Sequestration
Nonfunctioning lung without normal connection with functioning lung
Complex mass (solid, fluid, &/or cystic) in either lower lobe with systemic arterial supply
Helpful Clues for Rare Diagnoses
Hydatid (Echinococcal) Cyst
Endemic to Mediterranean, Africa, and Australia
“Meniscus” sign: Crescent of gas around endocyst
“Water lily” sign: Collapse of hydatid cyst; endocyst membrane floating in intact pericyst
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