Seminars in Roentgenology
Volume 45, Issue 1 , Pages 8-21, January 2010

Idiopathic Interstitial Pneumonias

  • Jeffrey P. Kanne, MD

      Affiliations

    • Corresponding Author InformationAddress reprint requests to Jeffrey P. Kanne, MD, Division of Cardiothoracic Imaging, Department of Radiology, University of Wisconsin-Madison, MC 3235, 600 Highland Ave, Madison, WI 53572

Division of Cardiothoracic Imaging, Department of Radiology, University of Wisconsin-Madison, Madison, WI

Article Outline

 

The idiopathic interstitial pneumonias (IIP) are a group of distinct clinicopathologic entities, “which are sufficiently different from one another to be designated as separate disease entities.”1

The IIPs are an evolving group of diseases having undergone several classification schemes. Liebow and Carrington2 described the histologic classification for chronic interstitial pneumonia in 1969. Other classifications were proposed by Katzenstein3 and Müller and Colby4 in 1997, in which lymphocytic interstitial pneumonia (LIP) and giant cell interstitial pneumonia were dropped. LIP was thought to be a lymphoproliferative disorder, which could progress to lymphoma. Many cases of giant cell interstitial pneumonia were subsequently recognized as hard metal pneumoconiosis from cobalt and tungsten carbide exposure. Additionally, the newly recognized interstitial pneumonias, such as respiratory bronchiolitis-associated interstitial lung disease (RB-ILD), bronchiolitis obliterans organizing pneumonia (BOOP), acute interstitial pneumonia (AIP), and nonspecific interstitial pneumonia (NSIP) were included in the classifications of the IIPs.

The most recent classification of the IIP is a joint statement of the American Thoracic Society (ATS) and European Respiratory Society (ERS) (Table 1).1 The level of evidence used to generate this statement and recommendations is largely that of expert opinions of pulmonologists, radiologists, and pathologists agreed on by group consensus. However, it provides the first international consensus for a combined clinical, radiologic, and pathologic approach to the classification of the distinct clinicopathologic entities that comprise the IIPs.

Table 1. Evolution of Classification of Idiopathic Interstitial Pneumonias
Liebow and Carrington (1969) (chronic forms)2Katzenstein (1997)3Müller and Colby (1997)4ATS/ERS (2001)1
Usual interstitial pneumoniaUsual interstitial pneumoniaUsual interstitial pneumoniaIdiopathic pulmonary fibrosis
Desquamative interstitial pneumoniaDesquamative interstitial pneumonia and/or respiratory bronchiolitis interstitial lung diseaseDesquamative interstitial pneumonia
Desquamative interstitial pneumonia

Respiratory bronchiolitis interstitial lung disease

Bronchiolitis obliterans interstitial pneumonia and diffuse alveolar damage Bronchiolitis obliterans organizing pneumoniaCryptogenic organizing pneumonia
Acute interstitial pneumoniaAcute interstitial pneumoniaAcute interstitial pneumonia
Nonspecific interstitial pneumoniaNonspecific interstitial pneumoniaNonspecific interstitial pneumonia⁎
Lymphoid interstitial pneumonia Lymphoid interstitial pneumonia
Giant cell interstitial pneumonia

⁎The ATS recently re-evaluated 67 patients with definite or probable idiopathic NSIP, which was designated as a “provisional diagnosis” in the 2001 classification system, and determined that idiopathic NSIP should remain a distinct clinicopathologic entity.5

High-resolution computed tomography (HRCT) of the chest is an integral component of the diagnostic process in diffuse lung diseases, particularly IIP. The primary role of HRCT is to group patients into those with usual interstitial pneumonia (UIP) and those without UIP. However, HRCT findings may be suggestive of other IIP or other diffuse lung disease.

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Idiopathic Pulmonary Fibrosis/Usual Interstitial Pneumonia 

The clinicopathologic entity of idiopathic pulmonary fibrosis (IPF) is the most common of the IIPs, accounting for approximately 40% of all idiopathic interstitial lung disease.6 It is strictly defined as “a specific form of chronic fibrosing interstitial pneumonia limited to the lung and associated with the histologic appearance of usual interstitial pneumonia.”7

IPF is an uncommon disease with estimated incidence and prevalence of 14.0-42.7 per 100,000 persons and 6.8-16.3 per 100,000 persons, respectively, in the United States.8 IPF occurs almost twice as frequently in men as in women, and prevalence and incidence in both sexes increase with age. Prognosis remains poor, with 5- and 10-year survival rates of 43% and 15%, respectively.9

By definition, the cause of IPF is unknown, but several potential causes or contributing factors have been identified, including viral infection (especially Ebstein-Barr virus),10, 11 occupational dust and fume exposure,12, 13 and genetic factors. Cigarette smokers have a slightly increased risk of developing IPF.14

Histologically, IPF is characterized by a pattern of UIP, the key features of which include architectural destruction, fibrosis usually with honeycombing, and scattered fibroblastic foci. The distribution of histopathologic abnormalities is patchy and involves the periphery of the acinus or lobule. Both temporal and spatial heterogeneity exist with foci of mature and developing fibrosis and alternating areas of fibrosis, interstitial inflammation, and normal lung.1

HRCT is central to establishing the diagnosis of IPF. The characteristic feature of UIP on HRCT is the presence of subpleural and basal predominant reticulation4, 15 (Fig. 1). Traction bronchiectasis or bronchiolectasis and architectural distortion may be present. Honeycomb cysts (Fig. 2) measuring 2-20 mm in size are present in up to 90% of patients at diagnosis.16, 17 Ground-glass opacity is common but, as a rule, is less extensive than the reticular abnormality. Like the spatial heterogeneity seen on histology, areas of normal lung may be interspersed within areas of abnormal lung. Mediastinal lymphadenopathy is present in up to 90% of patients and may increase as lung fibrosis progresses.18 Subsequent scans may show relatively rapid progression of fibrosis (Fig. 3), and imaging and pulmonary functional stability over several years may bring into the question the diagnosis of IPF.

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  • Figure 1. 

    A 68-year-old man with IPF. Transverse (A, B) and coronal (C) HRCT images show basal-predominant subpleural reticulation with architectural distortion and mild traction bronchiectasis (arrows). Ground-glass opacity is mild. The esophagus is patulous from presbyesophagus.

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  • Figure 2. 

    A 61-year-old man with IPF. Transverse (A, B) and coronal (C) HRCT images show extensive reticulation, architectural distortion, and honeycombing. A larger bulla or cyst is in the right lower lobe (arrow). Typical of IPF, the lung bases are the most severely affected.

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  • Figure 3. 

    A 58-year-old woman with IPF and declining respiratory function. HRCT images (A, B) show mild subpleural reticulation and mild ground-glass opacity. HRCT images 9 months later at the same levels (C, D) demonstrate progressive fibrosis characterized by increased reticulation and ground-glass opacity. A few honeycomb cysts have developed in the left lower lobe (arrows).

Patients with an acute exacerbation of IPF are acutely ill and hypoxic. HRCT shows diffuse ground-glass opacity superimposed on typical features of UIP (Fig. 4). Mortality rates are very high, and survivors are usually left with further respiratory functional impairment.

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  • Figure 4. 

    A 70-year-old man with an acute exacerbation of IPF. HRCT images (A, B) show basal-predominant reticulation, architectural distortion, and traction bronchiectasis with superimposed diffuse ground-glass opacity.

An experienced chest radiologist can make the diagnosis of UIP in 50%-70% of patients with IPF, and be correct in about 90% of cases.19, 20, 21 One study demonstrated a positive predictive value of 96% for IPF with a confident diagnosis of UIP on HRCT.22

The computed tomography (CT) pattern of UIP occurs in diseases other than IPF, such as asbestosis,1 collagen vascular disease (especially rheumatoid arthritis), chronic drug toxicity, sarcoidosis,23 and hypersensitivity pneumonitis can occur. The presence of poorly defined centrilobular nodules and sparing of the lung bases should raise the question of hypersensitivity pneumonitis, as these 2 findings are extremely unusual in IPF.24 Micronodules in a perilymphatic distribution (subpleural, peribronchial, perivenous) or large honeycomb cysts are suggestive of sarcoidosis.

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Nonspecific Interstitial Pneumonia 

Katzensten and Fiorelli first proposed the term NSIP to describe patients with interstitial lung disease whose lung biopsy specimens did not fit into any well-defined histologic pattern.3 These patients have a better prognosis than those with IPF, and this group of interstitial lung disease is distinct from the other IIPs. Many patients with an NSIP histology or characteristic HRCT findings have underlying connective tissue disease, such as progressive systemic sclerosis (scleroderma).

NSIP may also be idiopathic. The ATS and ERS declared NSIP to be a provisional diagnosis in their 2001 joint statement.1 However, the ATS recently re-evaluated 67 patients with definite or probable idiopathic NSPP and determined that idiopathic NSIP should remain a distinct clinicopathologic entity, which has an overall good prognosis, with 5- and 10-year survival rates of 80% and 73%, respectively.5 Of interest, 46% of patients in this cohort were from Asian countries, 67% were women, and 69% were never-smokers. A potential link to cigarette smoking has also been reported.25

Histologically, NSIP can be classified into 3 categories: primarily interstitial pneumonitis, both interstitial pneumonitis and fibrosis, and primarily fibrosis. Unlike UIP, the histologic features of NSIP are temporally homogeneous, and fibroblastic foci are absent.26

The hallmark of NSIP on HRCT is bilateral and symmetric ground-glass opacity27, 28 (Fig. 5). Peripheral and basal predominance is the most common distribution, occurring in more than half of the patients with histologically proven NSIP. Sparing of the subpleural lung may also occur.29 Superimposed fine subpleural reticulation, traction bronchiectasis, and architectural distortion are common and indicate fibrosis (Figure 6, Figure 7). Centrilobular nodules and honeycomb cysts are uncommon. NSIP can often be distinguished from UIP on the basis of the extent of ground-glass opacity and the absence of honeycombing, as the presence of honeycombing is strongly predictive of UIP.30 However, patients with idiopathic NSIP may, overtime, develop HRCT findings typical of UIP, such as honeycomb cysts, resulting in indistinguishable HRCT patterns (Fig. 8).31

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  • Figure 5. 

    A 43-year-old woman with idiopathic NSIP (cellular). Transverse (A, B) and coronal (C) HRCT images show symmetric, basal predominant ground-glass opacity with relative subpleural sparing.

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  • Figure 6. 

    A 65 -year-old woman with polymyositis and fibrotic NSIP. HRCT image (A) shows patchy ground-glass opacity and mild reticulation in the bases with relative subpleural sparing. HRCT image 2 years later (B) shows increased ground-glass opacity and reticulation indicative of progressive fibrosis.

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  • Figure 7. 

    A 57-year-old woman with scleroderma and fibrotic NSIP. Transverse (A) and coronal (B) HRCT images demonstrate basal-predominant ground-glass opacity and reticulation with traction bronchiectasis (arrows).

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  • Figure 8. 

    A 34 -year-old woman with scleroderma and advanced fibrotic NSIP. Transverse (A) and coronal (B) HRCT images show end-stage fibrosis with honeycombing and traction bronchiectasis in the mid and lower lungs. Note the dilated esophagus (arrow) from scleroderma.

Prognosis depends on whether fibrosis is present. Patients with the purely cellular form of NSIP have an excellent prognosis and usually respond to corticosteroid therapy.5, 9 However, these patients comprise a very small percentage of those with NSIP. Fibrotic NSIP has a better prognosis than IPF, but 10-year survival rate is only 35%.29 Some patients will have NSIP in 1 lobe and UIP in another on surgical lung biopsy. In this case, the prognosis is identical to that of IPF.32

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Cryptogenic Organizing Pneumonia 

Cryptogenic organizing pneumonia (COP) was described as a distinct clinicopathologic entity by Davison et al33 in 1983. Epler et al34 described the same entity under the name BOOP in 1985. Although the term BOOP became popular, COP is now the preferred term as it better describes the essential features of this entity and avoids confusion with diseases of the airways like constrictive bronchiolitis.

As the name implies, COP is characterized by patchy organizing pneumonia in the alveoli and alveolar ducts. Intraluminal polyps may be present in the bronchioles. A mild associated interstitial infiltrate is present with relative preservation of normal lung architecture.1

COP occurs equally among men and women with a mean age of 55 years at presentation. COP affects nonsmokers twice as frequently as smokers. Patients generally develop a prodrome of cough, with or without sputum production, similar to a lower respiratory tract infection. Constitutional signs and symptoms, such as fever and weight loss, often ensue. Elevated erythrocyte sedimentation rate (ESR) and C-reactive protein and peripheral neutrophilia are common.35, 36 Pulmonary function testing usually demonstrates mild to moderate restrictive physiology and moderately decreased diffusion capacity.

Lung consolidation is the cardinal finding on HRCT, occurring in at least 90% of patients with COP (Fig. 9). In about half of patients, lung consolidation has a subpleural, peribronchial, or perilobular distribution, and air bronchograms without or with cylindrical bronchial dilation are usually present in areas of lung consolidation (Fig. 10).37, 38 Ground-glass opacity occurs in about 60% of patients and is often patchy.39, 40 Nodules of varying sizes may be present and often are found in addition to lung consolidation. Although most nodules are smooth and well defined and measure < 10 mm in diameter, larger nodules with poorly defined margins may be present. Nodules demonstrating the “reverse halo” sign, defined as a focus of ground-glass opacity surrounded by a crescent or ring of consolidation, are highly suggestive of organizing pneumonia (Fig. 11),41, 42 although this sign has also been described in other entities, including Paracoccidioides brasiliensis infection43 and Wegener granulomatosis.44

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  • Figure 9. 

    A 57-year-old woman with COP. HRCT images through the mid (A) and lower (B) lungs show bilateral peribronchial consolidation with some peripheral ground-glass opacity. A perilobular distribution of consolidation (arrows) is also present in the lower lobes.

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  • Figure 11. 

    A 53-year-old man with COP. HRCT images (A, B) show left upper lobe consolidation with surrounding ground-glass opacity in addition to heterogeneous nodules with central ground-glass opacity and peripheral consolidation (reverse halo sign) (arrows).

Prognosis is generally good with most patients exhibiting complete recovery with corticosteroid therapy. However, about 15% of patients will have relapse of their disease,45 and a small number of patients will progress to lung fibrosis (Fig. 12) with honeycombing.46, 47

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  • Figure 12. 

    A 44-year-old woman with relapsing COP and fibrosis. HRCT image (A) shows peribronchial and perilobular consolidation. Patchy ground-glass opacity is in both lungs. HRCT image after corticosteroid therapy (B) demonstrates resolution of consolidation with increased consolidation and mild reticulation. HRCT image 1 year later (C) shows progressive reticulation and new traction bronchiectasis (arrow).

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Acute Interstitial Pneumonia 

AIP is rapidly progressive interstitial pneumonia characterized histologically by organizing diffuse alveolar damage. It is clinically similar to acute respiratory distress syndrome but, by definition, is idiopathic.48 It affects patients of any age, with a mean of about 50 years of age. Men and women are affected equally. There is no association with smoking. Often, patients may begin with an upper respiratory tract and constitutional symptoms suggestive of a viral syndrome, and develop progressive dyspnea on exertion and rapidly progressing pneumonia.48

Ground-glass opacity, traction bronchiectasis, and architectural distortion are the most common HRCT features.49 Ground-glass opacity is typically patchy with lobular sparing and is almost always bilateral (Fig. 13).50 Consolidation interlobular septal thickening, intralobular reticulation, and bronchovascular bundle thickening may be present in varying degrees. About 25% of patients with AIP will have an anteroposterior gradient in ground-glass opacity and consolidation with more extensive disease in the dependent lung (Fig. 14).1

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  • Figure 13. 

    A 39-year-old woman with AIP. Transverse HRCT image through upper lungs (A) shows patchy ground-glass opacity with sparing of some lobules. Coronal HRCT image (B) demonstrates heterogeneous ground-glass opacity and consolidation with more involvement of the lower lobes.

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  • Figure 14. 

    A 61-year-old man with AIP. HRCT images (A, B) shows an anterior-posterior gradient of ground-glass opacity and consolidation with more ground-glass opacity located anteriorly becoming more consolidative posteriorly. Mild bronchial dilation is present (arrows).

The prognosis of AIP is poor. Mechanical ventilation is usually necessary to sustain life. No proven treatment has been identified, and the mortality rate exceeds 50%. Survivors may develop chronic or recurrent interstitial pneumonia.51

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Respiratory Bronchiolitis-Associated Interstitial Lung Disease 

RB-ILD is included in the ATS/ERS IIP classification despite being invariably related to cigarette smoking.1 Although respiratory bronchiolitis is extremely common in most smokers and, by definition, results in no known clinical disease, RB-ILD is uncommon, suggesting host factors predispose an individual to develop interstitial lung disease when exposed to a significant amount of cigarette smoke.52, 53

Histologically, RB-ILD is characterized by a patchy, bronchiolocentric distribution of pigmented macrophages. These clusters of macrophages are limited to the respiratory bronchioles, alveolar ducts, and immediately adjacent alveoli. Mild peribronchial fibrosis extending into adjacent alveolar septa is present. Centrilobular emphysema is a common accompanying histologic finding.54

Most patients with RB-ILD present in the fourth or fifth decade of life, and average a 30 pack-year smoking history. Younger patients with RB-ILD tend to be heavier smokers (2-3 packs per day).1 Cough and mild dyspnea are common with mild restrictive physiology and mildly reduced diffusion capacity on pulmonary function tests. However, some patients may demonstrate airflow obstruction secondary to underlying pulmonary emphysema.55

HRCT findings of RB-ILD include poorly defined centrilobular nodules, patchy ground-glass opacity, and bronchial wall thickening (Figure 15, Figure 16).56 Many patients have centrilobular emphysema predominating in the upper lobes.52, 57 Patchy air trapping may also be present, characterized by hypoattenuating secondary pulmonary lobules that persist on expiratory computed tomography, a finding common but less extensive in nonsmokers. The amount of macrophage accumulation and chronic inflammation correlate with the extent of centrilobular nodules, and the degree of ground-glass opacity correlates with the quantity of macrophages within the alveoli and alveolar ducts.52, 57 The HRCT findings of RB-ILD overlap considerably with those of hypersensitivity pneumonitis and desquamative interstitial pneumonia (DIP). Exposure history may be helpful in distinguishing RB-ILD from HP. DIP and RB-ILD may be indistinguishable on HRCT; however, the extent of ground-glass opacity is greater with DIP, and centrilobular nodules are uncommon.57

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  • Figure 15. 

    A 47-year-old man with RB-ILD from heavy smoking. HRCT images (A, B) show numerous poorly defined centrilobular nodules and some patchy ground-glass opacity.

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  • Figure 16. 

    A 51-year-old female smoker with RB-ILD. Transverse (A, B) and coronal (C) HRCT images show diffuse heterogeneity of the lungs with extensive but patchy ground-glass opacity with sparing of some secondary lobules.

Prognosis after smoking cessation is excellent,57, 58 and development of extensive lung fibrosis has not been reported. However, the natural history of RB-ILD has yet to be elucidated.

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Desquamative Interstitial Pneumonia 

DIP is a rare interstitial pneumonia, which was initially thought to represent a precursor of UIP, characterized by the presence of numerous cells, believed to be sloughed type II pneumocytes, in the alveolar air spaces.2 However, these cells actually represent intra-alveolar macrophages.59 Despite the misnomer, the term DIP was retained in the 2001 ATS/ERS classification after much debate.1

Histologically, DIP is characterized by the presence of numerous macrophages in the alveolar airspaces. These macrophages often have brown pigment associated with cigarette smoking. The interlobular septa are thickened with a mild inflammatory infiltrate often composed of plasma cells and scattered eosinophils. Unlike respiratory bronchiolitis and RB-ILD, which have a bronchiolocentric distribution, the lungs are diffusely affected in DIP.1

The majority cases of DIP occur in smokers, and many authors believe RB-ILD and DIP to be a spectrum of the same process.54, 58, 60, 61 However, DIP has also been reported to rarely develop in nonsmokers after inhalation of particulate matter,62 passive exposure to cigarette smoke,60 nitrofurantoin therapy,63 and connective tissue disease. A DIP reaction may accompany other diseases, such as NSIP, pulmonary Langerhans cell histiocytosis, and carcinoma.64

Most patients with DIP are in their third or fourth decade of life at presentation, and about half present with cough and dyspnea on exertion. Pulmonary function tests usually reveal mild restrictive physiology but can be normal or can be accompanied by airflow obstruction. Reduced diffusion capacity is nearly universal.61

Bilateral ground-glass opacity is the primary finding of DIP on HRCT (Fig. 17). Ground-glass opacity can be diffuse, but involvement primarily of the middle and lower lung zones is more common. Approximately half of patients will have superimposed reticulation (Fig. 18), and honeycombing is present in less than one-third of patients. Architectural distortion, traction bronchiectasis, and small cysts may also be present in areas of ground-glass opacity.65

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  • Figure 17. 

    A 46-year-old female smoker with DIP. HRCT images (A, B) demonstrate patchy, basal-predominant ground-glass opacity with sparing of some secondary lobules, similar to findings in RB-ILD.

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  • Figure 18. 

    A 51-year-old woman with connective tissue disease and DIP. Transverse (A, B) and coronal (C) HRCT images show diffuse ground-glass opacity, with mild reticulation in the periphery of the lungs, particularly in the bases.

Prognosis is better than that of IPF, especially with smoking cessation and corticosteroid therapy, with a reported 10-year survival of 70%. However, the disease may progress despite smoking cessation.58, 60, 61

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Lymphoid Interstitial Pneumonia 

LIP, also referred to as lymphocytic interstitial pneumonitis, is characterized by a diffuse lymphocytic interstitial infiltrate.1 LIP continues to be the center of great debate, regarding its place in the IIP classification system. Initially, LIP was believed to be a precursor of lymphoma, but only a few cases of LIP have actually been shown to progress to a lymphoid malignancy.66, 67 Most affected patients are women with Sjögren syndrome. Idiopathic LIP is very uncommon, and some argue that LIP should be removed from the IIP classification and be defined as a form of lymphoid hyperplasia.1

Histologically, LIP shows a dense interstitial lymphoid infiltrate composed of lymphocytes, plasma cells, and histiocytes which predominantly involves the alveolar septa. An increased number of alveolar macrophages and hyperplasia of type II pneumocytes is usually associated, and lymphoid hyperplasia is usually present.1

Most patients with LIP present with signs and symptoms of their underlying systemic or autoimmune disease. Although LIP is most commonly associated with Sjögren syndrome,68 LIP may less commonly occur in the setting of other connective tissue diseases such as rheumatoid arthritis and systemic lupus erythematosis. LIP has also been associated with hepatic disorders such as chronic active hepatitis and primary biliary cirrhosis; immune disorders such as HIV infection (especially in children), severe combined immunodeficiency (SCID), autoimmune hemolytic anemia, hypogammaglobulinemia, pernicious anemia, and multicentric Castleman disease; and Hashimoto thyroiditis.

The typical HRCT findings of LIP are bilateral ground-glass opacity, thin-walled perivascular cysts, and poorly defined centrilobular nodules (Fig. 19).69, 70 Nodules may also be present in a peribronchial distribution, and some patients may have foci of lung consolidation. Mild reticulation occurs in about half of patients (Fig. 20) and frank honeycombing is present occasionally.71 Sometimes, nodules or small calcifications may develop within the cysts, a feature that may reflect amyloid deposition (Fig. 21).68

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  • Figure 19. 

    A 62-year-old woman with Sjögren syndrome and LIP. Transverse (A) and coronal (B) HRCT images demonstrate scattered, basal-predominant thin-wall cysts of varying sizes.

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  • Figure 20. 

    A 45-year-old woman with Sjögren syndrome and LIP. Transverse (A) and coronal (B) HRCT images show peripheral ground-glass opacity in the upper lungs, becoming more extensive in the mid and lower lungs. Scattered small cysts and superimposed reticulation are present.

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  • Figure 21. 

    A 57-year-old woman with Sjögren syndrome and LIP. HRCT image shows scattered thin-wall cysts. Additionally, calcium is present in some nodules and cysts (arrows) and is presumably related to amyloid deposition.

Patients with LIP may be treated with corticosteroids, which are believed to either improve or stabilize symptoms. However, more than one-third of patients will progress despite therapy and develop diffuse lung fibrosis, and it remains unknown as to whether treatment affects the natural course of the disease.

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Conclusions 

The IIPs comprise a complex and evolving group of distinct clinicopathologic entities. Ever since the first proposed classification in 1969, the IIPs have been surrounded with uncertainty, confusion, and great debate. Furthermore, the nomenclature and classification of IIPs will likely change in the future as more is learned about their respective pathophysiologies.

HRCT plays a key role in the diagnosis of IIP as the imaging features of the various IIPs are well described, and the radiologists may suggest an appropriate diagnosis with a high-degree of certainty. This is particularly true in the setting of IPF/UIP. However, considerable overlap in HRCT findings exists among the IIPs, and, thus, a multidisciplinary approach involving clinicians, radiologists, and pathologists is essential to establishing the most appropriate diagnosis.

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PII: S0037-198X(09)00068-6

doi:10.1053/j.ro.2009.07.004

Seminars in Roentgenology
Volume 45, Issue 1 , Pages 8-21, January 2010

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