000 Ground Glass Opacity Infiltrates

Ground-glass opacity (GGO) refers to a hazy area of increased lung density on CT imaging where the underlying vascular structures are still visible through the opacity. GGOs appear less dense than consolidations (which obscure underlying structures) and can have a variety of causes.
Ground-glass opacities are indicative of partial filling of air spaces, interstitial thickening (e.g., due to fluid, cells, or fibrosis), or a combination of both. They are nonspecific findings that can be associated with numerous conditions, including:
• Infections such as viral pneumonia (e.g., COVID-19), fungal infections, or atypical bacterial infections.
• Inflammatory diseases like organizing pneumonia or hypersensitivity pneumonitis.
• Edema from congestive heart failure or acute respiratory distress syndrome (ARDS).
• Neoplasia such as adenocarcinoma in situ (previously known as bronchioloalveolar carcinoma).
• Fibrotic lung disease or early stages of interstitial lung disease.
Evaluation of GGOs considers factors such as distribution, pattern, size, presence of associated findings (e.g., nodules, consolidations, fibrosis), and clinical context to determine their significance.
In a Nutshell
The Reason We See Things 
HOW MANY SQUARES 3 OR 4?
Courtesy Ashley Davidoff
How many squares
Ashley Davidoff thecommonvein.net notes scale music-0019-low resb

 

Filled and Half-Filled Alveoli – Differences in Appearance on CT
When the alveoli are fully filled with fluid, tumor, or pus for example, the overall net density will be white, and when adjacent to air filled airways, air bronchograms are visible (left side of image)
When the alveoli are only partially filled, the density of the fluid added to the density of the air results in an overall gray density, and when positioned next to air filled bronchi, there is insufficient contrast to create an air bronchogram and sufficient to enable visualization of the blood vessels. This is called ground glass opacification
Ashley Davidoff
TheCommonVein.net lungs-00681
Hazy areas of increased opacity or areas of increased attenuation with
preserved bronchial and vascular margins
Why is it called ground-glass?
Not black, not white but gray
The term has its origins in the way old movies shot their flashback scenes, through a ground-glass lens that gave the film a hazy appearance

Chest radiologists adopted it in the 1980s, with a first appearance in the Fleischner Society Glossary of Terms for Thoracic Radiology in 1984

Filled and Half-Filled Alveoli – Differences in Appearance on CT
When the alveoli are fully filled with fluid, tumor, or pus for example, the overall net density will be white, and when adjacent to air filled airways, air bronchograms are visible (left side of image)
When the alveoli are only partially filled, the density of the fluid added to the density of the air results in an overall gray density, and when positioned next to air filled bronchi, there is insufficient contrast to create an air bronchogram and sufficient to enable visualization of the blood vessels. This is called ground glass opacification
Ashley Davidoff
TheCommonVein.net
  • Gray areas of increase density arising from
    • Disease in the
      • airways
      •  alveoli
      •  inter-alveoalar septa
      •  interstitium
AIR BRONCHOGRAMS AND GROUND GLASS
TheCommonVein.net
The collage provides a perspective of disease of the small airways and the alveoli that results in ground glass appearance on Xray. A process that increases the density of the lungs to a net “gray” regional density will result in a ground glass opacity whether it is inflammation of the walls ((second column) fluid within the lumen of the small air ways and alveoli (3rd column) or whether it is fibrosis in the walls of the small airways or alveolar septa (last column alveoli. The net result on CT is a ground glass opacity (bottom row). In fibrosis there are secondary changes which include bronchiolectasis in this case, but other associated changes may include reticulations or centrilobular nodules
Ashley Davidoff MD TheCommonVein.net lungs-0733
Types of Fluid Accumulations and Appearance as Ground Glass Infiltrates
Ashley Davidoff MD TheCommonVein.net lungs-0702d- lo res
Ground Glass Opacity and Adenocarcinoma with Lepidic Growth
The Ground Glass Opacity (GGO) in this case  is  caused by partial filling of the alveolus with malignant cells                                                                                                                                                        Ground glass opacification may be caused by partial filling of the alveolus with cellular material resulting in  partial replacement of air with solid material.  The net density is gray rather than white in the situation where the  alveolus is fully replaced with cells or fluid. There is blending of the black of the subtending airways and  the white of the vessels  with the gray density of the cellular infiltrate and hence the normal vessels are not visualized in ground glass opacities.
Ashley Davidoff MD TheCommonVein.net 134375b01
Ground Glass Nodules and Pneumonic Infiltrate and Air Bronchograms
Ashley Davidoff
TheCommonVein.net

 

Normal Structure

Anatomy of the Distal Airways in Color and in the Black and White of Radiology
The subsegmental medium sized airways give rise to the terminal bronchiole (tb) which gives rise to the membranous airways. These include in order, the respiratory bronchiole (rb), alveolar duct (ad) and alveolar sac (as)
Ashley Davidoff TheCommonvein.net

 

  • Ground Glass Changes May result from Disease in the
    • Small Airways
    • Alveoli
    • Interalveolar Septa
    • Interstitium
The collage provides a persepective of disease of the small airways and the alveoli that results in ground glass appearance on Xray. A process that incereases the densityof the lungs to a net “gray”regional density will result in a ground glass opacity whether it is inflammation of the walls ((second column) fluid within the lumen of the small aireways and alveoli (3rd column) or whether it is fibrosis in the walls of the small airways or alveolar septa (last column alveoli. The net result on CT is a ground glass opacity (bottom row). In fibrosis there are secondarychanges which include bronchiolectasis in this case, butother associated changes may include reticulations or centrilobuar nodules
Ashley Davidoff MD TheCommonVein.net lungs-0733

Origin in the Alveoli

Types of Fluids that Can Partially Fill in the Alveoli

Types of Fluid Accumulations and Appearance as Ground Glass Infiltrates
Ashley Davidoff MD TheCommonVein.net lungs-0702d- lo res

Application to Radiology

Concept of the Fully Filled Alveolus with Net “White Density”
vs.
Half Filled Fluid Alveolus with  a Net of “Gray” Density

Filled and Half-Filled Alveoli – Differences in Appearance on CT
When the alveoli are fully filled with fluid, tumor, or pus for example, the overall net density will be white, and when adjacent to air filled airways, air bronchograms are visible (left side of image)
When the alveoli are only partially filled, the density of the fluid added to the density of the air results in an overall gray density, and when positioned next to air filled bronchi, there is insufficient contrast to create an air bronchogram and sufficient to enable visualization of the blood vessels. This is called ground glass opacification
Ashley Davidoff
TheCommonVein.net

Acute Ground Glass Infiltrates Caused by partial Filling of the Alveoli with Fluid 

Radiological Application This an eample of acute diffuse ground glass change where thenet density of the alveoli is gray caused by partial filling of the alveoli with fluid
Ashley Davidoff MD TheCommonVein.net
lungs-0708d- lo res

CHF

Acute  CHF
50 year old female with diabetes, chronic renal failure with congestive heart failure.  CT in the coronal plane shows diffuse ground glass changes, Kerley B lines at the right base, 
Ashley Davidoff MD TheCommonvein.net  50-003-CT
50 year old female with diabetes, chronic renal failure with congestive heart failure.  CT in the coronal plane shows diffuse ground glass changes, Kerley B lines  peribronchial cuffing in the right upper lobe and right lower lobe
Ashley Davidoff MD TheCommonvein.net  50-004-CT
50 year old female with diabetes, chronic renal failure with congestive heart failure.  CT in the axial plane shows diffuse ground glass changes, thickening of the interlobular septa,  centrilobular nodules  peribronchial cuffing  mosaic attenuation in the  right lower lobe, associated with a complex right sided effusion
Ashley Davidoff MD TheCommonvein.net  50-010-CT

 

Types of Cells  that Can Partially Fill in the Alveoli

Examples include Langerhans Cells, Macrophages, Eosinophils and Malignant Cells

  • Half Filled Cellular Accumulation in the Alveolus Type of Cells include Langerhans Cells Macrophages and Malignant Cells
    Ashley Davidoff MD TheCommonVein.net lungs-0707a
    Ground Glass Opacity (GGO) Caused by Cellular Accumulation  with Partial Filling of the Alveolus  Type of Cells include Langerhans Cells Macrophages and Malignant Cells
    Ground glass opacification may be caused by partial filling of the alveolus with cellular material with partial replacement of air with solid material with the net density being gray rather than white if the alveolus were fully filled. The black of the airway nor the white of the vessels may blend with the gray density and hence they are not visualised in ground glass opacities. ore is usually lood vessels and  airway walls  The replacement may be due to cellular infiltration including inflammatory ,benign or malignant cells without or with fluid.
    Ashley Davidoff MD TheCommonVein.net lungs-0707ad

    Eosinophils in Acute Eosinophilic Pneumonia

    Infiltration of eosinophils and exudation into the alveoli and interalveolar septa and interstitium
    Ashley Davidoff TheCommonVein.net
    lungs-0756b01

    Application to Radiology

Concept of the Fully Filled Alveolus with Net “White Density”
vs.
Half Filled Fluid Alveolus with  a Net of “Gray” Density

Ground Glass as a result of Cellular Accumulations in the Alveoli
When there are extensive cellular accumulations in the alveoli, such as adenocarcinoma with lepidic growth, Langerhans cells or other macrophages, the overall net density of the region of involvement will be gray, and when adjacent to the black air filled airways, a ground glass appearance will be apparent
Ashley Davidoff
TheCommonVein.net
ssb = subsegmental bronchiole
tb = terminal bronchiole
rb = respiratory bronchiole
as = alveolar duct
as = alveolar sac
is = interalveolar septum
lungs-00682-lo res

 

 

 

 

 

 

 

  • Difference Between Consolidation and Ground Glass
AIR BRONCHOGRAMS AND GROUND GLASS
TheCommonVein.net

 

GGO -(Nodule)  in Adenocarcinoma with Lepidic Growth 

Ground Glass Opacity and Adenocarcinoma with Lepidic Growth
The Ground Glass Opacity (GGO) in this case  is  caused by partial filling of the alveolus with malignant cells                                                                                                                                                        Ground glass opacification may be caused by partial filling of the alveolus with cellular material resulting in  partial replacement of air with solid material.  The net density is gray rather than white in the situation where the  alveolus is fully replaced with cells or fluid. There is blending of the black of the subtending airways and  the white of the vessels  with the gray density of the cellular infiltrate and hence the normal vessels are not visualized in ground glass opacities.
Ashley Davidoff MD TheCommonVein.net 134375b01

 

 

GGO with Origins in the Interstitium

Ground Glass as a result of Interstitial Disease –
When there are extensive interstitial fibrotic changes in the interstitial compartments of the lung which include the and the interalveolar septa, and the supporting interstitium of the lung between the acini and small airways, the overall net density of the region of involvement will be gray, and when adjacent to the black air filled airways, a ground glass appearance will be apparent
Ashley Davidoff
TheCommonVein.net
ssb = subsegmental bronchiole
tb = terminal bronchiole
rb = respiratory bronchiole
as = alveolar duct
as = alvelar sac
is = anteralveolar septum
lungs-00682-lo res

Ground Glass from Interlobular Septal Fibrosis

Ground glass and interlobular septal fibrosis post COVID Infection
Ashley Davidoff MD TheCommonVein.net
Ground glass and interlobular septal fibrosis post COVID Infection
Ashley Davidoff MD TheCommonVein.net
Ground glass and interlobular septal fibrosis post COVID Infection
Ashley Davidoff MD TheCommonVein.net
Ground glass and interlobular septal fibrosis post COVID Infection
Ashley Davidoff MD TheCommonVein.net
Ground glass and interlobular septal fibrosis post COVID Infection
Ashley Davidoff MD TheCommonVein.net
Ground glass and interlobular septal fibrosis post COVID Infection
Ashley Davidoff MD TheCommonVein.net
Ground glass and interlobular septal fibrosis post COVID Infection
Ashley Davidoff MD TheCommonVein.net
Ground glass and interlobular septal fibrosis post COVID Infection
Ashley Davidoff MD TheCommonVein.net

Combination of Elements resulting in ground Glass Changes

In Acute Eosinophilic Pneumonia Changes include;
Alveolar, and Interalveolar Interstitial Infiltration with Eosinophils and Inflammatory Exudate 

The ground glass changes are a combination of the cellular and exudative inflammatory response in the small airways, alveoli, interalveolar septa and interstitium, and thickened alveolar septum

Alveolar and Interalveolar Interstitial Infiltration with Eosinophils and Inflammatory Exudate – Ground Glass Changes
The ground glass changes are a combination of the cellular and exudative inflammatory response in the small airways, alveoli, interalveolar septa and interstitium, and thickened alveolar septum
The diagram shows the abnormal secondary lobule (a) The involved components include the small airways(b) alveoli and interalveolar interstitium (c) and the thickened interlobular septum (d) surrounding the secondary lobule due to an inflammatory process, cellular infiltrate and congestion of the venules and lymphatics in the septum.  An anatomic specimen of a secondary lobule from a patient with thickened interlobular septa and interstitial thickening is shown in image e, and is overlaid in red (f) . A magnified view of an axial  CT of the lungs in a patient with acute eosinophillic pneumonia shows thickened interlobular septa and centrilobular nodules (g) The inflammatory changes in the aforementioned structures result in an overall increase in density of the lung manifesting as ground glass changes (g) and overlaid in red (h) 
Ashley Davidoff MD The CommonVein.net  lungs-0762
Infiltration of eosinophils and exudation into the alveoli and interalveolar septa and interstitium
Ashley Davidoff TheCommonVein.net
lungs-0756b01
Ground Glass Opacity
On HRCT, ground glass opacity appears as hazy areas of increased opacity or attenuation with preserved anatomy, including bronchial and vascular margins.7 In comparison, ground glass opacity is less opaque than consolidation.7

    • A region of ground glass opacity on CT with it’s incidental correlation on T2 weighted MRI showing that in this instance it is composed of water
      Ashley Davidoff MD
      TheCommonvein.net
  • Diseases Associated with GGO
  • Types of GGO

    There are several types of GGO. These include:

      • Nodules
      • Focal
      • Diffuse
          • Subsegmental 
          • Segmental
          • Lobar
          • Patchy
          • Central
      • Halo
      • Reversed Halo
      • Head Cheese

      Focal

      • Nodules and Nodular: This type can indicate both benign and malignant conditions. GGO that persists over several scans may indicate either premalignant or malignant growths.
        • Centrilobular: This type appears within one or several lobules of the lung. Lobules are the hexagonal divisions of the lung. The connective tissue between the lobules is unaffected.
        • 41-year-old man with subacute hypersensitivity pneumonitis. High-resolution CT image shows bilateral poorly defined centrilobular nodules and ground-glass opacities. Also evident are lobular areas (arrows) of decreased attenuation.

          Intralobular

        • WEGENER’S GRANULOMATOSIS WITH POLYANGIITIS, GPA,VASCULITIS AND MICROINFARCTION
          81-year-old male with weight loss, renal failure, and hemoptysis
          CT axial view (a) shows multiple peripheral wedge shaped ground glass densities subtended by distended feeding vessels (a,b,c, red arrowheads) reflecting areas of microinfarction due to vasculitis that affects both the arterioles and venules.
          Priscilla Slanetz MPH MD
          TheCommonVein.net

          • 26 male SOB s/p RFA ablation for atrial fibrillation lung pulmonary let upper lobe pulmonary vein thrombosed secondary lobule interlobular septa are thickened secondary lobule due to congestion and hemorrhage dx pulmonary vein thrombosis secondary to radiofrequency ablation therapy iatrogenic CTscan Courtesy Ashley Davidoff MD Scott Tsai MD ground glass changes pulmonary infarction venous infarction
            TheCommonVein.net
        • Diffuse:
          • Diffuse opacities show up in multiple lobes of one or both lungs. This pattern occurs when the air in the lungs is replaced with fluid, inflammation, or damaged tissue.
            • Segmental
            • Subsegmental
            • Lobar
        • Subsegmental
            • COVID 19
              55-year-old male presents with a fever and a cough.
              CXR findings reveal vague peripheral, bibasilar, “ground glass” changes in the lower lung zones.
              The CT scan confirms the presence of bilateral, predominantly basilar, nodular, and peripheral mixes ground glass and consolidative opacifications consistent with the diagnosis of COVID 19. Differential diagnosis however includes other viral pneumonias, allergic alveolitis and other multifocal and organizing pneumonias.
              Courtesy Kevin Chang MD
              TheCommonVein.net

              PET Positive Adenocarcinoma in a Background of Multicentric  Adenocarcinoma with Lepidic Growth
              The CT is from a 51 year old male who is a smoker who shows a ground glass opacity (GGO) mixed with a solid mass (arrow in a) and multicentric BAC in a lower cut (b) characterised by three areas in the right lower lobe of  partial alveolar opacification.  Ground glass appearance is the result of partial opacification of the alveoli. Two of the GGOs measure close to 2cms each and the third more anterior measures about 8mms. In this instance a PET scan was positive in the area (green ring in d) It is likely that the solid component in image a represents the transformation of BAC – (really a carcinoma in situ) into adenocarcinoma.
              Courtesy Ashley Davidoff MD
              TheCommonVein.net
              87769c02b.8s
    •  Subsegmental 
      • HEAD CHEESE SIGN, GROUND GLASS, MOSAIC PATTERN
        SARCOIDOSIS, STAGE IV, PTX, ENCASEMENT
        Ashley Davidoff MD
        SLE AND PE
        24 year old male with SLE presented with chest pain and dyspnea and initial CT showed occlusive pulmonary emboli to the right lower lobe (a,b, red arrowhead) with total occlusion of the right lobe artery extending into posterior basal segmental vessels (red ring d compared with normal vessels surrounded by white rin (d). An associated wedge shaped ground glass region is noted (e,f red arrowhead) representing either hemorrhage or early infarction
        Ashley Davidoff MD
        Ground Glass Nodules with ? Lymphangitic Spread
        Ashley Davidoff
        TheCommonVein.net
        60 year old female who presents with hemoptysis. Ct scan shows a focal region of ground glass change in the superior segment of the left lower lobe, abutting the fissure, likely reflecting hemorrhage
        Ashley Davidoff MD TheCommonVein.net

         

        Segmental

          • Lobar or Almost Lobar

          • 44-year-old male presents with history of sarcoidosis manifesting as diffuse ground glass involving the upper lobes and lower lobes sparing the middle lobe and lingula to some extent.


    • SARCOIDOSIS, STABLE DIFFUSE GROUND GLASS AND ADENOPATHY OVER 9 YEARS
      Ashley Davidoff MD

      SARCOIDOSIS, STABLE DIFFUSE GROUND GLASS AND ADENOPATHY OVER 9 YEARS
      Ashley Davidoff MD

    • Multilobar

BASILAR GROUND GLASS INFILTRATES
Axial CT through the base of the lungs show diffuse ground glass density, with some segmental sparing in the middle lobe and lingula characterized by increased density without obscuring the airways and vessels
Ashley Davidoff MD TheCommonVein.net 
    • CHF
  • DIFFUSE GROUND DISEASE WITH REGIONS OF NORMAL LUNG
    CHF, INTERSTITIAL EDEMA KERLEY A and B
    Ashley Davidoff MD TheCommonVein.net
    • Diffuse Multilobar with Mosaic Attenuation : This pattern develops when small arteries or airways within the lung are blocked. The opaque areas vary in intensity.
    • Hypersensitivity Pneumonitis
      High-resolution CT: increase in density in areas of ground glass and air trapping in lower lobes in patients with hypersensitivity pneumonitis
      Courtesy Mluisamtz11
      SECONDARY PULMONARY LOBULE
      lung pulmonary lobule secondary lobule arteriole venule interlobular septa bronchovascular bundle mosaic pattern air trapping fx ground glass XCTscan
      Davidoff MD
    • Diffuse Multilobar with Crazy paving: Crazy paving shows up as a linear pattern. It can occur when the spaces between the lobules widen.
    • CRAZY PAVING
      57-year-old female with progressive dyspnea.
      CXR shows bilateral, diffuse alveolar opacities having a perihilar and basal distribution with sparing of the apices
      CT shows diffuse ground glass change with crazy paving morphology characterized by bilateral diffuse ground-glass opacities (GGO) with interlobular and intralobular septal thickening. There is a geographical distribution .
      Differential diagnosis
      ARDS
      PCP pneumonia
      CHF
      Alveolar Hemorrhage
      UIP
      Hypersensitivity Pneumonitis
      XRT pneumonitis
      COP
      Chronic Eosinophilic
      Lymphangitis
      Veno-Occlusive Disease
      Ashley Davidoff MD
      TheCommonVein.net

       

    • Crazy-paving sign. Axial CT of the chest shows thickening of the intralobular and interlobular septa with a superimposed background of ground-glass opacity in a patient with pulmonary alveolar proteinosis.
      Source
      Signs in Thoracic Imaging
      Journal of Thoracic Imaging 21(1):76-90, March 2006.

      Congestion of the Venules in the Interlobular Septa

Halo Sign in Angioinvasive Aspergillosis

Focal Wedge Shaped

ANCA VASCULITIS WITH PULMONARY INFARCTION AND MYOCARDIAL INFARCTION   CT scan of a 67 year old female with anca  vasculitis shows regions of dystrophic calcification in the lateral aspect of the right lower lobe (white arrow, a and b) )with focal nodular parenchymal consolidation, that likely reflects a site of prior small vessel infarct. Dystrophic calcification in the LV myocardium (blue arrows c) and a suggestion of fatty dysplasia in the left ventricular apex red arrow d) suggest changes from small vessel infarct.  Ashley Davidoff MD

Multicentric Mixed
ACUTE ALVEOLAR PNEUMONITIS
PA and lateral chest X-ray of a 54 year old female with SLE shows bibasilar ground glass infiltrates.
The heart is slightly enlarged and the region of the IVC on the lateral examination is also enlarged
Ashley Davidoff MD
key word
acute pneumonitis
SLE
ACUTE ALVEOLAR PNEUMONITIS
CT scan through the 4 chambers of the heart using lung windows is from a a 54 year old female with SLE. Recent CXR showed bibasilar ground glass infiltrates.
The scan shows basilar multicentric infiltrates with elements of ground glass change and small airway wall thickening (red circles in the right lower lobe middle lobe and lingula, as well as interlobular septal thickening (green circle) in the lateral basal segment of the left lower lobe. A small pericardial effusion is present (yellow arrowhead)
Ashley Davidoff MD

GROUND GLASS MORPHOLOGY IN ILD
Ground glass infiltrates are one of the features of the interstitial disease with increased density without obscuring the airways and vessels
    • Focal Associated with Other Diseases
    • Halo sign:
    • This type of opacity fills the area around the nodules.

    • WEGENER’S GRANULOMATOSIS WITH POLYANGIITIS, GPA, HALO SIGN AND AIR BRONCHOGRAMS
      81-year-old male with weight loss, renal failure, and hemoptysis
      CT axial view (a) shows a 2 cm solid nodule in the RUL surrounded by A HALO SIGN OF GROUND GLASS CHANGES AND RETICULAR CHANGES (a,b, red arrowheads), indicating surrounding hemorrhage, and subtle air bronchograms (a,b,c, teal arrowheads) best appreciated in c with narrowed windows.
      Priscilla Slanetz MPH MD
    • HEMORRHAGE, GROUND GLASS, HALO SIGN, AIR BRONCHOGRAM AND CHEERIO SIGN, WEGENER’S GRANULOMATOSIS WITH POLYANGIITIS, GPA.
      57 year old male presents with a history of hemoptysis and dyspnea.
      Axial CT scans show multicentric nodular consolidations with air bronchograms (red arrowheads a ,b, c), ground glass infiltrate (black arrowheads, a,b,c) halo sound around nodules and masses in the RLL (a,e, green arrowheads) and in the LLL 9a,f, blue arrowheads). Lastly there is a cheerio sign (a,d, white arrowheads) either representing granulomatous mass surrounding an airway, or central cavitation of a nodule.
      Ashley Davidoff MD.
      57 year old male presents with a history of hemoptysis and dyspnea.
      Axial CT scans show multicentric nodular consolidations with air bronchograms (red arrowheads a ,b, c), ground glass infiltrate (black arrowheads, a,b,c) halo sound around nodules and masses in the RLL (a,e, green arrowheads) and in the LLL 9a,f, blue arrowheads). Lastly there is a cheerio sign (a,d, white arrowheads) either representing granulomatous mass surrounding an airway, or central cavitation of a nodule.
      Ashley Davidoff MD TheCommonVein.net

       

    • Reversed halo sign: A reversed halo sign is an area that is almost totally surrounded by liquid-filled tissue.

    Hemorrhage

    Pre and Post Biopsy  – Hemorrhage and Pneumothorax Post Biopsy of an Adenocarcinoma
    Ashley Davidoff MD TheCommonVein.net
    70m – adenocarcinoma-
  • Diffuse Disease
CAUSES
    • normal expiration
    • partial filling of air spaces
    • partial collapse of alveoli
    • interstitial thickening
    • inflammation
    • edema
    • fibrosis
    • lepidic proliferation of neoplasm

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