Multiple Ill-Defined Nodules
Jonathan H. Chung, MD
DIFFERENTIAL DIAGNOSIS
Common
Pneumonia
Mycobacterial
Fungal
Bacterial
Metastases (Typically Hemorrhagic)
Bronchoalveolar Cell Carcinoma
Septic Emboli
Hypersensitivity Pneumonitis
Less Common
Wegener Granulomatosis
Silicosis/Coal Worker’s Pneumoconiosis
Pulmonary Langerhans Cell Histiocytosis
Pulmonary Infarcts
Kaposi Sarcoma
Sarcoidosis (Alveolar Type)
Rare but Important
Rheumatoid Nodules
Lymphoma
ESSENTIAL INFORMATION
Key Differential Diagnosis Issues
Clinical correlation paramount given large overlap of imaging manifestations
Helpful Clues for Common Diagnoses
Pneumonia
Acute clinical presentation in most cases: Fever, chills, malaise
Mycobacterial or fungal pneumonia may be indolent
Angioinvasive fungal pneumonia in immunosuppressed patients, often with neutropenia
Reactive lymphadenopathy common
Cavitary lung nodules and central low-attenuation lymphadenopathy: Tuberculous or fungal pneumonia
Metastases (Typically Hemorrhagic)
Variable-sized pulmonary nodules preferentially in peripheral and lower lungs
Ill-defined metastases on radiographs usually hemorrhagic
Choriocarcinoma, renal cell carcinoma, melanoma
CT often shows solid central nodule surrounded by halo of ground-glass opacity
Feeding artery sign: Pulmonary artery branches extend to nodules, implying hematogenous spread
Bronchoalveolar Cell Carcinoma
Subtype of adenocarcinoma with good prognosis relative to other types of lung cancer
Focal or multifocal ground-glass, mixed, or solid pulmonary nodules
Internal air bronchograms, cystic lucencies, or pseudocavitation
Chronic consolidation or ground-glass opacity, which mimics pneumonia; may be multifocal
Septic Emboli
Multiple, peripheral, and basilar consolidation or nodules with early cavitation
Feeding artery sign: Pulmonary artery branches extend to nodules, implying hematogenous spread
Loculated pleural effusion common
Hypersensitivity Pneumonitis
Allergic reaction to inhaled organic dust or chemicals
Geographic or centrilobular ground-glass opacities in all patients; air-trapping common
“Head-cheese” sign: Geographic regions of air-trapping, ground-glass opacities, and normal lung
Helpful Clues for Less Common Diagnoses
Wegener Granulomatosis
Multiple bilateral 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
Silicosis/Coal Worker’s Pneumoconiosis
Small, upper lobe preponderant centrilobular and perilymphatic nodules with appropriate exposure history
Progressive massive fibrosis: Small nodules coalesce into elliptical upper lobe masses with adjacent emphysema
Superimposed mediastinal and hilar lymphadenopathy; ± eggshell calcification
Pulmonary Langerhans Cell Histiocytosis
Multiple upper and mid lung subcentimeter pulmonary nodules in smoker
Typically centrilobular, ill defined, spares costophrenic angles
Multiple cysts; thin or thick walled; may be bizarre in shape
Other concomitant smoking-related conditions
Centrilobular emphysema, respiratory bronchiolitis, lung cancer, desquamative interstitial pneumonitis
Pulmonary Infarcts
Most often from pulmonary arterial embolism
Often in setting of superimposed cardiac dysfunction (cardiomyopathy, congestive heart failure)
Lower lung predominant, peripheral/subpleural, wedge-shaped consolidation
Reverse halo configuration (central ground-glass opacity with surrounding rim of consolidation) not uncommon
Resolves over months, retaining its original shape, rather than patchy resolution as in pneumonia
Kaposi Sarcoma
Peribronchovascular or perihilar, ill-defined, flame-shaped consolidation or nodules in patients with AIDS
Vast majority with pulmonary disease have cutaneous involvement
Mediastinal and hilar lymphadenopathy with avid contrast enhancement
Sarcoidosis (Alveolar Type)
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