Ground-Glass Opacities



Ground-Glass Opacities


Eric J. Stern, MD



DIFFERENTIAL DIAGNOSIS


Common



  • Atypical Pneumonia



    • Pneumocystis Pneumonia


    • Viral Pneumonia


  • Acute Airspace



    • Cardiogenic Pulmonary Edema


    • Noncardiac Pulmonary Edema


    • Diffuse Alveolar Hemorrhage (DAH)


    • Hypersensitivity Pneumonitis (HP)


    • Eosinophilic Pneumonia


  • Chronic Infiltrative Lung Disease



    • Nonspecific Interstitial Pneumonitis


    • Smoking-Related Interstitial Lung Disease



      • Respiratory Bronchiolitis


      • Desquamative Interstitial Pneumonia (DIP)


    • Eosinophilic Pneumonia


Less Common



  • Bronchioloalveolar Cell Carcinoma


  • Atypical Adenomatous Hyperplasia (AAH)


Rare but Important



  • Pulmonary Alveolar Proteinosis (PAP)


  • Drug Reaction


ESSENTIAL INFORMATION


Key Differential Diagnosis Issues



  • Definition of ground-glass opacity (GGO)



    • Hazy increased lung density with preservation of underlying vessels


  • Recognition problems



    • Difficult if minimal or diffuse; pitfalls



      • Normally seen with exhalation


      • Volume averaging with thick collimation (> 5 mm)


      • Window settings too narrow or too wide


      • Normal in dependent lung from atelectasis


  • Radiology-pathology correlation



    • Partial airspace filling by edema, hemorrhage, infection, or tumor


    • Interstitial thickening by inflammation, edema, or fibrosis



      • Presence of consolidation suggests that GGO represents alveolar filling


      • GGO with reticular opacities or traction bronchiectasis likely represents interstitial disease


    • Lepidic growth: Abnormal cells use alveolar septa and respiratory bronchioles as scaffolding to grow



      • Preserves lung architecture and often results in GGO


Helpful Clues for Common Diagnoses



  • Atypical Pneumonia



    • Typically febrile immunocompromised patients, GGO should be considered opportunistic infection


  • Cardiogenic Pulmonary Edema



    • GGO earliest parenchymal change, usually gravity-dependent distribution


    • Increased severity → septal thickening, consolidation, and pleural effusions


  • Noncardiac Pulmonary Edema



    • Acute respiratory distress syndrome (ARDS)


    • GGO predominant abnormality, extent typically > 50% of lung


  • Diffuse Alveolar Hemorrhage (DAH)



    • Lobular GGO often admixed with dense consolidation, gravity dependent


    • Hemorrhage may be associated with focal lesions, resulting in halos



      • Hemorrhagic metastases (e.g., renal cell carcinoma)


      • Invasive aspergillosis


      • Transbronchial biopsy site


  • Hypersensitivity Pneumonitis (HP)



    • Typically diffuse; centrilobular ground-glass nodules 70%


    • Most specific pattern: Geographic GGO + normal lung + air-trapping (head cheese sign)


  • Eosinophilic Pneumonia



    • Acute



      • Pattern identical to acute pulmonary edema


      • GGO (100%) admixed with septal thickening, consolidation, random distribution


      • Pleural effusions common (80%)


    • Chronic



      • Typical distribution: Peripheral and upper lobes


      • Consolidation > ground-glass opacities


      • Often migratory, waxing and waning over time


  • Nonspecific Interstitial Pneumonitis



    • Idiopathic or associated with collagen vascular diseases



    • GGO often basilar, follow bronchovascular pathways (fan- or wedge-shaped)


    • Traction bronchiectasis often out of proportion to severity of reticular opacities


  • Smoking-Related Interstitial Lung Disease



    • Spectrum of cigarette-related injuries from respiratory bronchiolitis to DIP



      • Generally dose related; more common with heavier cigarette smoking or use of unfiltered cigarettes


    • Respiratory bronchiolitis: Upper lobe centrilobular GGO


    • DIP: GGO in 100%, often diffuse, symmetric, and panlobular


Helpful Clues for Less Common Diagnoses



  • Bronchioloalveolar Cell Carcinoma



    • GGO may be focal, typically lobulated, and sharply demarcated from surrounding lung


    • GGO may be combined with solid nodular tissue (part-solid nodule)


    • Most helpful characteristic is growth or presence of solid component within GGO


  • Atypical Adenomatous Hyperplasia (AAH)



    • 3% of population; prevalence increases with age (7% over 60 years)


    • Importance unknown but may represent premalignant lesion



      • Prevalence of AAH in surgical specimens of patients with adenocarcinoma or bronchioloalveolar cell carcinoma (BAC) high (25%)


    • Imaging features that help differentiate between BAC and AAH



      • Air bronchograms; larger size associated with BAC


      • Sphericity associated with AAH


Helpful Clues for Rare Diagnoses

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Aug 8, 2016 | Posted by in CARDIOLOGY | Comments Off on Ground-Glass Opacities

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