Lung Mass > 3 cm
Jonathan H. Chung, MD
DIFFERENTIAL DIAGNOSIS
Common
Lung Cancer
Lung Metastases
Pneumonia
Mycobacterial Pneumonia
Fungal Pneumonia
Lung Abscess
Pseudotumor
Rounded Atelectasis
Less Common
Pulmonary Arteriovenous Malformation
Hematoma
Bronchogenic Cyst
Sequestration
Cystic Adenomatoid Malformation
Rare but Important
Pulmonary Vein Varix
Hydatid Cyst (Echinococcal Disease)
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
High likelihood of malignancy in pulmonary lesions > 3 cm
Margins
Benign lesions: Smooth margins
Malignant lesions: Multilobular, spiculated margins (corona radiata), or pleural tail
Clinical history essential in suggesting correct radiological diagnosis
History of smoking, asbestos exposure, or pulmonary fibrosis: Primary lung cancer
Previous malignancy: Metastatic disease
Appropriate exposure history: Endemic fungal/mycobacterial/parasitic infection
Helpful Clues for Common Diagnoses
Lung Cancer
Most common malignant cause of death
Adenocarcinoma most common
Most common in upper lung zone (2/3 of primary lung cancers)
Spiculated margins, pleural tail, thick-walled cavitation
Hilar and mediastinal lymphadenopathy
Lung Metastases
Metastases more common in lower lung zones due to increased blood flow
Usually multiple, variable sizes, and well marginated
Large single metastasis to lungs: Colon cancer, sarcomas, breast cancer, renal cell carcinoma, melanoma
Large metastases also in testicular cancer, ovarian cancer, and head and neck cancers, though usually multiple
Mycobacterial Pneumonia
Most cases in adults post primary, upper lung consolidation, which may cavitate
Tuberculoma
Fungal Pneumonia
Immunosuppressed patients susceptible to invasive aspergillosis
Endemic fungi: Histoplasma and Blastomyces in Ohio and Mississippi River valleys, Coccidioides in desert southwestern USA
Lung Abscess
Irregular, thick-walled cavity; air-fluid level; gravity-dependent portions of lungs secondary to aspiration
Pseudotumor
Loculated pleural effusion in pulmonary fissure
Common among patients with congestive heart failure
Lenticular opacity in fissure
Most commonly in minor fissure
Margins of pseudotumor taper along course of pulmonary fissure
Can be multiple
Rounded Atelectasis
Definitive diagnosis on CT requires 4 findings
Pleural abnormality: Pleural thickening, pleural effusion, or pleural plaque
Broad-based attachment of mass-like consolidation to pleural abnormality
Volume loss
Comet tail (or hurricane) sign: Swirling of bronchovasculature into mass-like consolidation
Helpful Clues for Less Common Diagnoses
Pulmonary Arteriovenous Malformation
Lobulated nodule with feeding artery and vein diagnostic
Lower lung predominance
Associated with Osler-Weber-Rendu syndrome (hereditary hemorrhagic telangiectasis)
Embolization or surgery considered if feeding artery ≥ 3 mm in diameter
Hematoma
Blood filling pulmonary laceration secondary to blunt or penetrating trauma
More common in younger patients
In blunt trauma, often initially obscured by adjacent contusion on radiographs; readily evident on CT
Bronchogenic Cyst
Pulmonary bronchogenic cysts less common than mediastinal bronchogenic cysts
Usually medial lower lobes
Fluid density, round and well defined
Usually asymptomatic and incidental
Infection of bronchogenic cysts: Rapid increase in size, development of air or air-fluid levels
Sequestration
Nonfunctioning lung, which does not have normal connection with functioning lung
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