DOI: 10.1148/rg.261055070
RadioGraphics 2006;26:59-77
© RSNA, 2006
Pneumoconiosis: Comparison of Imaging and Pathologic Findings1
Semin Chong, MD,
Kyung Soo Lee, MD,
Myung Jin Chung, MD,
Joungho Han, MD,
O Jung Kwon, MD and
Tae Sung Kim, MD
1 From the Department of Radiology and Center for Imaging Science (S.C., K.S.L., M.J.C., T.S.K.), Department of Pathology (J.H.), and Division of Pulmonary and Critical Care Medicine, Department of Medicine (O.J.K.), Samsung Medical Center, Sungkyunkwan University School of Medicine, 50 Ilwon-dong, Kangnam-ku, Seoul 135–710, Korea. Presented as an education exhibit at the 2004 RSNA Annual Meeting. Received March 29, 2005; revision requested April 27 and received May 20; accepted May 23. Supported by the SRC/ERC program of MOST/KOSEF (R11–2002-103). All authors have no financial relationships to disclose.
Address correspondence to K.S.L. (e-mail: kyungs.lee{at}samsung.com).
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Abstract
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Pneumoconiosis may be classified as either fibrotic or nonfibrotic, according to the presence or absence of fibrosis. Silicosis, coal worker pneumoconiosis, asbestosis, berylliosis, and talcosis are examples of fibrotic pneumoconiosis. Siderosis, stannosis, and baritosis are nonfibrotic forms of pneumoconiosis that result from inhalation of iron oxide, tin oxide, and barium sulfate particles, respectively. In an individual who has a history of exposure to silica or coal dust, a finding of nodular or reticulonodular lesions at chest radiography or small nodules with a perilymphatic distribution at thin-section computed tomography (CT), with or without eggshell calcifications, is suggestive of silicosis or coal worker pneumoconiosis. Magnetic resonance imaging is helpful for distinguishing between progressive massive fibrosis and lung cancer. CT and histopathologic findings in asbestosis are similar to those in idiopathic pulmonary fibrosis, but the presence of asbestos bodies in histopathologic specimens is specific for the diagnosis of asbestosis. Giant cell interstitial pneumonia due to exposure to hard metals is classified as a fibrotic form of pneumoconiosis and appears on CT images as mixed ground-glass opacities and reticulation. Berylliosis simulates pulmonary sarcoidosis on CT images. CT findings in talcosis include small centrilobular and subpleural nodules or heterogeneous conglomerate masses that contain foci of high attenuation indicating talc deposition. Siderosis is nonfibrotic and is indicated by a CT finding of poorly defined centrilobular nodules or ground-glass opacities.
© RSNA, 2006
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LEARNING OBJECTIVES FOR TEST 3
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After reading this article and taking the test, the reader will be able to:
- Recognize imaging features that help differentiate pneumoconiosis from other interstitial lung diseases.
- Correlate imaging findings with clinicopathologic findings in the various types of pneumoconiosis.
- Classify cases of pneumoconiosis as fibrotic or nonfibrotic.
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Introduction
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Pneumoconiosis is caused by the accumulation of inhaled particulates and involves a reaction of tissue in the lung (1). The International Labour Organization (ILO) has established a standardized system for classifying radiographic abnormalities in pneumoconiosis on the basis of the presence of the following lung parenchymal and pleural abnormalities: small rounded opacities, small irregular opacities, profusion of opacities, large opacities, zonal distribution of opacities (upper, middle, and/or lower), and pleural thickening (diffuse or circumscribed) (2). Although this standardized system has not helped define the clinical or pathologic entities of pneumoconiosis, it has been useful for epidemiologic purposes. Pneumoconiosis may be clinicopathologically classified as fibrotic (involving focal nodular or diffuse fibrosis) or nonfibrotic (involving particle-laden macrophages, with minimal or no fibrosis) (3). Silicosis, coal worker pneumoconiosis, asbestosis, berylliosis, and talcosis are fibrotic forms of pneumoconiosis. Siderosis (from iron oxide), stannosis (from tin oxide), and baritosis (from barium sulfate) are nonfibrotic forms of the disease. Silicosis, coal worker pneumoconiosis, and asbestosis are the three most common types of pneumoconiosis, whereas berylliosis, siderosis, stannosis, and baritosis are relatively uncommon. The article surveys the imaging findings in common and uncommon types of pneumoconiosis and provides clinicopathologic comparisons.
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Silicosis
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Silicosis is caused by the inhalation of fine particles of crystalline silicon dioxide (silica) (4). Quartz is the most common form of crystalline silica but is less fibrogenic than tridymite or cristbalite. Occupations such as mining, quarrying, and tunneling are associated with silicosis (5). The disease occurs in two clinical forms: acute silicosis, which manifests as alveolar silicoproteinosis; and classic silicosis, which manifests as chronic interstitial reticulonodular disease. Cases of classic silicosis may be classified as either simple or complicated, according to the radiographic findings (4). Simple silicosis is defined by a radiographic pattern of small and round or irregular opacities, whereas complicated silicosis, or progressive massive fibrosis, is characterized by large conglomerate opacities (1).
Carcinoma and tuberculosis are potential serious complications of silicosis (3). The development of carcinoma or tuberculosis is a strong independent predictor of mortality in patients with silicosis (6). Pulmonary symptoms such as dyspnea become increasingly severe as the radiologic abnormalities worsen with carcinoma or tuberculosis (7).
Acute Silicosis (Silicoproteinosis)
Acute exposure to silica dust, an occupational hazard for sandblasters, can result in the filling of the airspace in the lung with proteinaceous material (8). Histopathologic specimens of acute silicosis show severe alveolitis and alveolar filling with a substance that tests positive at periodic acid–Schiff staining, a finding consistent with alveolar lipoproteinosis (Fig 1). In this respect, acute silicosis is quite different from the classic form of the disease.
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Figure 1a. Acute silicosis in a 52-year-old man who worked for 10 years as a crystal craftsman. (a, b) Axial thin-section CT scans (1.0-mm-thick sections) obtained at the levels of the ventricles (a) and the left basal truncal bronchus (b) show ground-glass opacities and mild interlobular septal thickening (arrows) in the middle and lower lobes of the right lung and in the lingular division of the upper lobe of the left lung, respectively. (c) Photomicrograph (original magnification, x40; hematoxylin-eosin stain) of a specimen obtained with video-assisted thoracoscopic biopsy in the lingula shows a fine granular eosin-ophilic material that fills the alveolar space. Note the pigment-laden perivascular and interstitial macrophages and giant cells (arrows).
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Figure 1b. Acute silicosis in a 52-year-old man who worked for 10 years as a crystal craftsman. (a, b) Axial thin-section CT scans (1.0-mm-thick sections) obtained at the levels of the ventricles (a) and the left basal truncal bronchus (b) show ground-glass opacities and mild interlobular septal thickening (arrows) in the middle and lower lobes of the right lung and in the lingular division of the upper lobe of the left lung, respectively. (c) Photomicrograph (original magnification, x40; hematoxylin-eosin stain) of a specimen obtained with video-assisted thoracoscopic biopsy in the lingula shows a fine granular eosin-ophilic material that fills the alveolar space. Note the pigment-laden perivascular and interstitial macrophages and giant cells (arrows).
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Figure 1c. Acute silicosis in a 52-year-old man who worked for 10 years as a crystal craftsman. (a, b) Axial thin-section CT scans (1.0-mm-thick sections) obtained at the levels of the ventricles (a) and the left basal truncal bronchus (b) show ground-glass opacities and mild interlobular septal thickening (arrows) in the middle and lower lobes of the right lung and in the lingular division of the upper lobe of the left lung, respectively. (c) Photomicrograph (original magnification, x40; hematoxylin-eosin stain) of a specimen obtained with video-assisted thoracoscopic biopsy in the lingula shows a fine granular eosin-ophilic material that fills the alveolar space. Note the pigment-laden perivascular and interstitial macrophages and giant cells (arrows).
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Radiographic findings consist of bilateral consolidation and/or ground-glass opacities, which tend to appear in perihilar regions. Findings at thin-section computed tomography (CT) include numerous bilateral centrilobular nodular ground-glass opacities, multifocal patchy ground-glass opacities, and consolidation (8,9) (Fig 1 ), features that indicate the intraalveolar accumulation of proteinaceous material (9). Sometimes, a crazy-paving appearance (airspace filling and interlobular septal thickening) caused by the presence of edematous or fibrous tissue may be seen at thin-section CT (Fig 1).
The clinical course of acute silicosis is usually progressive and ends in death due to cor pulmonale and respiratory failure despite medical therapy with corticosteroids (10).
Classic Silicosis
Histopathologically, silicotic nodules are composed of mature collagen in the central portion, with a peripheral zone of particle-laden macrophages that appears markedly different from the surrounding lung parenchyma. In color, the nodules range from slate gray to dense black, depending on the mineral contents in the silica dust (1,11). A number of birefringent silicate crystals 1–3 µm in length usually can be identified at the cellular level with the use of polarized light microscopy (Fig 2) (12).
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Figure 2a. Classic silicosis in a 53-year-old man who worked for 12 years in sandblasting. Photomicrographs (original magnification, x100; hematoxylin-eosin stain) show a transbronchial lung biopsy specimen. (a) Image obtained with visible light shows intraalveolar aggregation of pigmented macrophages (arrows). (b) Image obtained with polarized light shows scattered interstitial silica particles (arrows).
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Figure 2b. Classic silicosis in a 53-year-old man who worked for 12 years in sandblasting. Photomicrographs (original magnification, x100; hematoxylin-eosin stain) show a transbronchial lung biopsy specimen. (a) Image obtained with visible light shows intraalveolar aggregation of pigmented macrophages (arrows). (b) Image obtained with polarized light shows scattered interstitial silica particles (arrows).
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Simple Form.—
On chest radiographs, simple silicosis is characterized by multiple nodular opacities that are well defined and uniform in shape and attenuation and that range from 1 to 10 mm in diameter (1) (Fig 3). These nodules are distributed throughout both lungs, but they tend to be predominantly located in the upper lobe and posterior portion of the lung (13) (Figs 3, 4). Calcification of nodules is seen on chest radiographs in 10%–20% of patients (1).
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Figure 3a. Silicosis in a 54-year-old man who worked for 20 years as a stonecutter. (a) Chest radiograph shows multiple small nodules in both lungs, predominantly in the upper and middle zones. (b) Axial thin-section CT scan (2.5-mm-thick section) obtained at the level of the aortic arch shows multiple small nodules with similar shape and attenuation throughout the upper lobes of both lungs.
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Figure 3b. Silicosis in a 54-year-old man who worked for 20 years as a stonecutter. (a) Chest radiograph shows multiple small nodules in both lungs, predominantly in the upper and middle zones. (b) Axial thin-section CT scan (2.5-mm-thick section) obtained at the level of the aortic arch shows multiple small nodules with similar shape and attenuation throughout the upper lobes of both lungs.
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Figure 4a. Silicosis in a 56-year-old man who worked for 25 years as a stonecutter. (a) Chest radiograph shows multiple variable-sized nodular lesions in both lungs, predominantly in the upper and middle zones. (b) Axial thin-section CT scan (1.0-mm-thick section) obtained at the level of the azygos arch shows multiple small nodules with a perilymphatic (centrilobular plus subpleural) distribution in the upper lobe of both lungs. Note the tendency toward coalescence of the nodules in the lung periphery (arrows).
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Figure 4b. Silicosis in a 56-year-old man who worked for 25 years as a stonecutter. (a) Chest radiograph shows multiple variable-sized nodular lesions in both lungs, predominantly in the upper and middle zones. (b) Axial thin-section CT scan (1.0-mm-thick section) obtained at the level of the azygos arch shows multiple small nodules with a perilymphatic (centrilobular plus subpleural) distribution in the upper lobe of both lungs. Note the tendency toward coalescence of the nodules in the lung periphery (arrows).
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At CT, the most characteristic feature of simple silicosis is the presence of multiple small nodules 2–5 mm in diameter (Figs 3, 4), accompanied by calcifications (14). The nodules in simple silicosis tend to be more sharply defined than those in coal worker pneumoconiosis but are otherwise indistinguishable from the latter at thin-section CT (14). The nodules may be distributed diffusely throughout both lungs, but they tend to be most numerous in the upper lobe, as shown on radiographs. At thin-section CT, nodules are usually observed in centrilobular, paraseptal, and subpleural regions and have a perilymphatic distribution (Figs 3, 4). Subpleural nodules have a rounded or triangular configuration, and if they are confluent, they may resemble pleural plaques (14) (Fig 4).
Hilar and mediastinal lymph node enlargement may precede the appearance of parenchymal nodular lesions. Calcification of lymph nodes is common and typically occurs at the periphery of the node. The so-called eggshell calcification pattern is highly suggestive of silicosis (Fig 5).
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Figure 5. Simple silicosis in a 60-year-old man who worked for 12 years in a tungsten mine. Thin-section CT scan (1.0-mm-thick section) obtained with mediastinal window settings at the level of the bronchus intermedius shows eggshell calcifications (arrows) in the hilar and subcarinal lymph nodes.
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Complicated Form.—
Complicated silicosis, also known as progressive massive fibrosis, develops through the expansion and confluence of individual silicotic nodules. At histopathologic analysis, a large conglomerate lesion, composed of multiple foci of central hyalinized collagen and a surrounding pigmented rim of macrophages, is observed. Focal necrosis is common in the central portions of the lesion and is occasionally associated with granulomatous inflammation (as in tuberculous infection) (1) (Fig 6).
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Figure 6a. Silicotuberculosis in a 52-year-old man who worked for 30 years as a stoneworker. (a) Axial thin-section CT scan (1.0-mm-thick section) obtained at the level of the great vessels shows an irregular thick-walled cavitary lesion (arrow) in the upper lobe of the left lung, a finding suggestive of pulmonary tuberculosis, as well as subpleural nodular lesions in both lungs. (b) CT scan obtained at the level of the main bronchi depicts bilateral conglomerate masses (arrows), multiple small centrilobular and subpleural nodules, and enlarged mediastinal lymph nodes (arrowheads) in the right lower paratracheal and left peribronchial areas.
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Figure 6b. Silicotuberculosis in a 52-year-old man who worked for 30 years as a stoneworker. (a) Axial thin-section CT scan (1.0-mm-thick section) obtained at the level of the great vessels shows an irregular thick-walled cavitary lesion (arrow) in the upper lobe of the left lung, a finding suggestive of pulmonary tuberculosis, as well as subpleural nodular lesions in both lungs. (b) CT scan obtained at the level of the main bronchi depicts bilateral conglomerate masses (arrows), multiple small centrilobular and subpleural nodules, and enlarged mediastinal lymph nodes (arrowheads) in the right lower paratracheal and left peribronchial areas.
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On chest radiographs, complicated silicosis usually is indicated by large symmetric bilateral opacities with a diameter of more than 1 cm and with an irregular margin (Figs 7, 8). The large opacities result from nodule coalescence and are observed commonly in the middle lung zone or peripheral one-third of the lung on axial chest images and in the upper lung zone on longitudinal images. The large opacities gradually migrate toward the hilum, leaving emphysematous lung tissue between the fibrotic tissue and the pleural surface (1). The CT features of progressive massive fibrosis are focal soft-tissue masses, often with irregular or ill-defined margins and calcifications, surrounded by areas of emphysematous change (15,16) (Figs 7, 8). The lateral interface of the mass typically parallels the lateral chest wall (17) (Fig 7). Occasionally, cavitation secondary to ischemic necrosis may occur in a mass.
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Figure 7a. Silicosis and progressive massive fibrosis in a 58-year-old man who worked for 30 years as a stoneworker. (a) Chest radiograph shows multiple small nodules and masses in both lungs, predominantly in the upper and middle zones, and eggshell calcifications (arrows) in the lung hilum and the mediastinum. (b) Axial thin-section CT scan (1.0-mm-thick section) obtained at the level of the aortic arch shows large symmetric bilateral opacities with irregular margins (arrows) indicative of progressive massive fibrosis, as well as numerous small nodules and septal thickening (arrowheads).
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Figure 7b. Silicosis and progressive massive fibrosis in a 58-year-old man who worked for 30 years as a stoneworker. (a) Chest radiograph shows multiple small nodules and masses in both lungs, predominantly in the upper and middle zones, and eggshell calcifications (arrows) in the lung hilum and the mediastinum. (b) Axial thin-section CT scan (1.0-mm-thick section) obtained at the level of the aortic arch shows large symmetric bilateral opacities with irregular margins (arrows) indicative of progressive massive fibrosis, as well as numerous small nodules and septal thickening (arrowheads).
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Figure 8a. Silicosis and progressive massive fibrosis in a 66-year-old man who worked for 10 years crushing rock with a high quartz content. (a) Chest radiograph shows large bilateral opacities (arrows) in the upper zones of the lung, as well as upward elevation of both hila. (b) Coronal CT scan (2.0-mm-thick section) obtained with mediastinal window settings shows bilateral conglomerate masses with calcifications (arrows), findings that represent progressive massive fibrosis in the upper zone of both lungs.
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Figure 8b. Silicosis and progressive massive fibrosis in a 66-year-old man who worked for 10 years crushing rock with a high quartz content. (a) Chest radiograph shows large bilateral opacities (arrows) in the upper zones of the lung, as well as upward elevation of both hila. (b) Coronal CT scan (2.0-mm-thick section) obtained with mediastinal window settings shows bilateral conglomerate masses with calcifications (arrows), findings that represent progressive massive fibrosis in the upper zone of both lungs.
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Silicotuberculosis
Pulmonary tuberculosis occurs in 25% of patients with acute or classic silicosis, and men with silicosis have a relative risk of tuberculosis that is 2.8 times that for men without silicosis (18). Radiologic features of silicotuberculosis include asymmetric nodules or consolidation, cavitation, and rapid disease progression (Fig 6). Of these features, cavitation is the strongest indicator of probable silicotuberculosis, although cavitation also may be caused by ischemic changes in a silicotic fibrotic mass.
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Coal Worker Pneumoconiosis
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Coal worker pneumoconiosis is caused by exposure to washed coal, which is nearly free of silica, and it has a histologic basis that is very different from that of silicosis. Tissue specimens from patients with coal worker pneumoconiosis demonstrate two characteristic morphologic features: coal macules (Fig 9) and progressive massive fibrosis (Fig 10). The latter is indicated by the presence of a fibrotic mass with a diameter of more than 1 cm and with anthracotic pigmentation. The coal macules range in size from 1 to 5 mm and are characterized by solid anthracotic pigmentation without intervening fibrotic tissue (Fig 9) (19). The macules contain pigment-laden macrophages that surround the bronchioles in the lobular core; thus, the distribution of the macules is primarily centrilobular. Despite these histopathologic differences, the radiologic findings in coal worker pneumoconiosis and those in silicosis are similar, and the two diseases cannot be easily distinguished from one another on images.
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Figure 9a. Coal worker pneumoconiosis in a 62-year-old man who worked for 20 years in a coal mine. (a) Axial thin-section CT scan (1.0-mm-thick section) obtained at the level of the aortic arch shows numerous small centrilobular (arrows) and subpleural (arrowheads) nodules in both lungs. (b) Photomicrograph (original magnification, x40; hematoxylin-eosin stain) of a pathologic specimen obtained with a transbronchial lung biopsy shows multiple nodules (arrows) and anthracotic pigmentation in the bronchovascular bundles.
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Figure 9b. Coal worker pneumoconiosis in a 62-year-old man who worked for 20 years in a coal mine. (a) Axial thin-section CT scan (1.0-mm-thick section) obtained at the level of the aortic arch shows numerous small centrilobular (arrows) and subpleural (arrowheads) nodules in both lungs. (b) Photomicrograph (original magnification, x40; hematoxylin-eosin stain) of a pathologic specimen obtained with a transbronchial lung biopsy shows multiple nodules (arrows) and anthracotic pigmentation in the bronchovascular bundles.
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Figure 10a. Progressive massive fibrosis in a 64-year-old man who worked for 25 years as a coal miner. (a) Axial thin-section CT scan (1.0-mm-thick section) obtained at the level of the aortic arch shows an irregularly marginated mass in the upper lobe of the right lung and multiple small subpleural and fissural nodules (arrows) in both lungs. (b) Contrast material–enhanced CT scan (5.0-mm-thick section) at a level similar to that in a, obtained with mediastinal window settings, shows a central necrotic area of low attenuation (arrows) in the mass. (c) Photograph of lobectomy specimen shows regions of central necrosis (arrows) within the black-pigmented parenchyma.
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Figure 10b. Progressive massive fibrosis in a 64-year-old man who worked for 25 years as a coal miner. (a) Axial thin-section CT scan (1.0-mm-thick section) obtained at the level of the aortic arch shows an irregularly marginated mass in the upper lobe of the right lung and multiple small subpleural and fissural nodules (arrows) in both lungs. (b) Contrast material–enhanced CT scan (5.0-mm-thick section) at a level similar to that in a, obtained with mediastinal window settings, shows a central necrotic area of low attenuation (arrows) in the mass. (c) Photograph of lobectomy specimen shows regions of central necrosis (arrows) within the black-pigmented parenchyma.
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Figure 10c. Progressive massive fibrosis in a 64-year-old man who worked for 25 years as a coal miner. (a) Axial thin-section CT scan (1.0-mm-thick section) obtained at the level of the aortic arch shows an irregularly marginated mass in the upper lobe of the right lung and multiple small subpleural and fissural nodules (arrows) in both lungs. (b) Contrast material–enhanced CT scan (5.0-mm-thick section) at a level similar to that in a, obtained with mediastinal window settings, shows a central necrotic area of low attenuation (arrows) in the mass. (c) Photograph of lobectomy specimen shows regions of central necrosis (arrows) within the black-pigmented parenchyma.
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The risk of tuberculosis is increased in individuals with coal worker pneumoconiosis, as it is in those affected by silicosis. Coal dust inhalation also is related to the development of chronic obstructive pulmonary disease, which contributes to increased mortality among patients with coal worker pneumoconiosis (20). Workers with a high degree of progressive massive fibrosis also have a significantly increased mortality rate (21).
Simple Form.—
The radiographic pattern of simple coal worker pneumoconiosis typically consists of small round nodular opacities and occasionally includes reticular or reticulonodular opacities (1). The nodules in coal worker pneumoconiosis have a diameter of 1–5 mm and tend to be less well defined at the margins and more granular in appearance than those found in silicosis (Fig 9). Calcifications are observed on chest radiographs in 10%–20% of patients. Calcification develops as a central nodular dot in coal worker pneumoconiosis, whereas it tends to be more diffuse in silicosis (22,23). Furthermore, the eggshell calcification pattern that is pathognomonic of simple silicosis is uncommon in simple coal worker pneumoconiosis (it is observed in only 1.3% of patients) (22).
The CT features of coal worker pneumoconiosis are similar to those of silicosis. Small nodules may be observed diffusely throughout the lungs, typically with a perilymphatic distribution but sometimes with a centrilobular predominance, but they tend to be most numerous in the upper lung zone (Fig 9). At CT, calcification is observed within the nodules in 30% of patients with the disease. Moreover, hilar or mediastinal lymph node enlargement also is reported in 30% of patients (24).
Complicated Form.—
On chest radiographs, large opacities (progressive massive fibrosis) may be seen in complicated coal worker pneumoconiosis, as in complicated silicosis (Fig 6). However, the histopathologic basis of these features in complicated coal worker pneumoconiosis is different from that in complicated silicosis. In coal worker pneumoconiosis, the fibrotic mass consists of haphazardly arranged collagen with numerous pigment-laden macrophages and with abundant free pigment especially evident in the central region. Foci of frank necrosis, cholesterol clefts, and chronic inflammatory cellular infiltrates also are often present (25) (Fig 10).
Fibrotic masses in complicated coal worker pneumoconiosis are defined according to the regularity of the lesion border and the pattern of the surrounding parenchyma (25). Most such lesions have an irregular border with associated surrounding pericicatricial emphysema (Fig 10). However, some have a regular border without pericicatricial emphysema.
It is clinically and radiologically important to differentiate progressive massive fibrosis from lung cancer. Matsumoto et al (26) reported that magnetic resonance (MR) imaging is potentially useful for this purpose. On MR images, lung cancer appears as a high-signal-intensity lesion on T2-weighted images (Fig 11), whereas progressive massive fibrosis appears as a low-signal-intensity abnormality when compared with the signal intensity of muscle on both T1- and T2-weighted images (Fig 12). Some investigators have suggested that the most common MR characteristics of progressive massive fibrosis are signal isointensity on T1-weighted images and hypointensity on T2-weighted images, in comparison with the signal intensity in skeletal muscle. Moreover, with an intravenously administered MR contrast medium, the lesion in progressive massive fibrosis appears peripherally enhanced more frequently than not (27). Thus, the signal intensity manifested on T2-weighted images provides a clue for the differentiation of lung cancer from progressive massive fibrosis. When a mass lesion is depicted with high signal intensity on T2-weighted MR images, the finding is highly suggestive of lung cancer, and histopathologic analysis should be performed for diagnosis (Fig 11).
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Figure 11a. Lung cancer and coal worker pneumoconiosis in a 68-year-old man who worked for 20 years in a coal mine. (a) Axial CT scan (5.0-mm-thick section) obtained at the level of the left basal truncal bronchus shows a well-defined 2-cm-diameter nodule (arrow) in an upper segment of the lower lobe of the left lung, a finding that represents a combined neuroendocrine large cell carcinoma and adenocarcinoma, as well as multiple smaller nodules (arrowheads). (b) T2-weighted MR image obtained at a level similar to that in b shows the high-signal-intensity nodule (arrow) in the lower lobe. (c) Integrated positron emission tomographic (PET)-CT scan shows a high uptake of fluorine 18 fluorodeoxyglucose (FDG) (arrow) in the nodule, a finding suggestive of malignancy. (d) Photograph of a gross specimen obtained at left lower lobectomy shows the cancer (arrow) and multiple black-pigmented nodules (arrowheads) in the lung parenchyma and pleural surface.
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Figure 11b. Lung cancer and coal worker pneumoconiosis in a 68-year-old man who worked for 20 years in a coal mine. (a) Axial CT scan (5.0-mm-thick section) obtained at the level of the left basal truncal bronchus shows a well-defined 2-cm-diameter nodule (arrow) in an upper segment of the lower lobe of the left lung, a finding that represents a combined neuroendocrine large cell carcinoma and adenocarcinoma, as well as multiple smaller nodules (arrowheads). (b) T2-weighted MR image obtained at a level similar to that in b shows the high-signal-intensity nodule (arrow) in the lower lobe. (c) Integrated positron emission tomographic (PET)-CT scan shows a high uptake of fluorine 18 fluorodeoxyglucose (FDG) (arrow) in the nodule, a finding suggestive of malignancy. (d) Photograph of a gross specimen obtained at left lower lobectomy shows the cancer (arrow) and multiple black-pigmented nodules (arrowheads) in the lung parenchyma and pleural surface.
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Figure 11c. Lung cancer and coal worker pneumoconiosis in a 68-year-old man who worked for 20 years in a coal mine. (a) Axial CT scan (5.0-mm-thick section) obtained at the level of the left basal truncal bronchus shows a well-defined 2-cm-diameter nodule (arrow) in an upper segment of the lower lobe of the left lung, a finding that represents a combined neuroendocrine large cell carcinoma and adenocarcinoma, as well as multiple smaller nodules (arrowheads). (b) T2-weighted MR image obtained at a level similar to that in b shows the high-signal-intensity nodule (arrow) in the lower lobe. (c) Integrated positron emission tomographic (PET)-CT scan shows a high uptake of fluorine 18 fluorodeoxyglucose (FDG) (arrow) in the nodule, a finding suggestive of malignancy. (d) Photograph of a gross specimen obtained at left lower lobectomy shows the cancer (arrow) and multiple black-pigmented nodules (arrowheads) in the lung parenchyma and pleural surface.
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Figure 11d. Lung cancer and coal worker pneumoconiosis in a 68-year-old man who worked for 20 years in a coal mine. (a) Axial CT scan (5.0-mm-thick section) obtained at the level of the left basal truncal bronchus shows a well-defined 2-cm-diameter nodule (arrow) in an upper segment of the lower lobe of the left lung, a finding that represents a combined neuroendocrine large cell carcinoma and adenocarcinoma, as well as multiple smaller nodules (arrowheads). (b) T2-weighted MR image obtained at a level similar to that in b shows the high-signal-intensity nodule (arrow) in the lower lobe. (c) Integrated positron emission tomographic (PET)-CT scan shows a high uptake of fluorine 18 fluorodeoxyglucose (FDG) (arrow) in the nodule, a finding suggestive of malignancy. (d) Photograph of a gross specimen obtained at left lower lobectomy shows the cancer (arrow) and multiple black-pigmented nodules (arrowheads) in the lung parenchyma and pleural surface.
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Figure 12a. Progressive massive fibrosis in a 59-year-old man who worked for 20 years in a coal mine. (a) Composite of axial thin-section CT scans (1.0-mm-thick sections) obtained at various levels of the distal trachea shows irregularly marginated 20–30-mm nodules (arrows) accompanied by smaller satellite nodules and surrounding reticulation in the upper lobe of both lungs. (b) T1-weighted MR image obtained at a level close to that in a shows the slightly hyperintense lesions (arrows) in both upper lobes. (c) T2-weighted MR image obtained at a similar level shows an absence of signal at the lesion sites and a small pleural effusion (arrowheads) in the right lung. (d) Integrated PET-CT scan shows increased uptake of FDG in both nodules (straight arrows) and in a right paratracheal lymph node (curved arrow).
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Figure 12b. Progressive massive fibrosis in a 59-year-old man who worked for 20 years in a coal mine. (a) Composite of axial thin-section CT scans (1.0-mm-thick sections) obtained at various levels of the distal trachea shows irregularly marginated 20–30-mm nodules (arrows) accompanied by smaller satellite nodules and surrounding reticulation in the upper lobe of both lungs. (b) T1-weighted MR image obtained at a level close to that in a shows the slightly hyperintense lesions (arrows) in both upper lobes. (c) T2-weighted MR image obtained at a similar level shows an absence of signal at the lesion sites and a small pleural effusion (arrowheads) in the right lung. (d) Integrated PET-CT scan shows increased uptake of FDG in both nodules (straight arrows) and in a right paratracheal lymph node (curved arrow).
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Figure 12c. Progressive massive fibrosis in a 59-year-old man who worked for 20 years in a coal mine. (a) Composite of axial thin-section CT scans (1.0-mm-thick sections) obtained at various levels of the distal trachea shows irregularly marginated 20–30-mm nodules (arrows) accompanied by smaller satellite nodules and surrounding reticulation in the upper lobe of both lungs. (b) T1-weighted MR image obtained at a level close to that in a shows the slightly hyperintense lesions (arrows) in both upper lobes. (c) T2-weighted MR image obtained at a similar level shows an absence of signal at the lesion sites and a small pleural effusion (arrowheads) in the right lung. (d) Integrated PET-CT scan shows increased uptake of FDG in both nodules (straight arrows) and in a right paratracheal lymph node (curved arrow).
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Figure 12d. Progressive massive fibrosis in a 59-year-old man who worked for 20 years in a coal mine. (a) Composite of axial thin-section CT scans (1.0-mm-thick sections) obtained at various levels of the distal trachea shows irregularly marginated 20–30-mm nodules (arrows) accompanied by smaller satellite nodules and surrounding reticulation in the upper lobe of both lungs. (b) T1-weighted MR image obtained at a level close to that in a shows the slightly hyperintense lesions (arrows) in both upper lobes. (c) T2-weighted MR image obtained at a similar level shows an absence of signal at the lesion sites and a small pleural effusion (arrowheads) in the right lung. (d) Integrated PET-CT scan shows increased uptake of FDG in both nodules (straight arrows) and in a right paratracheal lymph node (curved arrow).
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PET is useful for distinguishing benign abnormalities from malignancies, but its role in the diagnosis of malignancy in the setting of pneumoconiosis remains unclear. Intensive uptake of FDG may occur in the fibrotic mass in progressive massive fibrosis (Fig 12 ), and the observation of resultant mass enhancement on images may lead to confusion of progressive massive fibrosis with lung cancer (28) (Figs 11, 12).
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Asbestosis
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Asbestosis is diffuse interstitial pulmonary fibrosis that occurs secondary to the inhalation of asbestos fibers (29). It is considered separately from other asbestos-related diseases, such as benign pleural effusion and plaques, malignant mesothelioma, and bronchogenic carcinoma. Asbestos is a term that is used to describe several fibrous silicate minerals that may be classified into two groups: serpentine and amphibole. Materials that contain asbestos (eg, chrysotile, crocidolite, and amosite) are widely used in industry for their tensile strength and heat resistance (11).
At histopathologic analysis, asbestos bodies, which may consist of a single asbestos fiber surrounded by a segmented protein-iron coat, can be identified in intraalveolar macrophages (30) (Fig 13).
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Figure 13. Asbestos body. Photomicrograph (original magnification, x1000; hematoxylin-eosin stain) shows a translucent asbestos fiber (straight arrow) surrounded by a segmented protein-iron coat that is much more prominent around the lower part of the fiber, and an alveolar macrophage (curved arrow).
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Asbestosis manifests with the same clinical, radiologic, and histopathologic features as other forms of diffuse interstitial pulmonary fibrosis. Nevertheless, according to criteria established by the American Thoracic Society (31), asbestosis may be diagnosed without lung biopsy in the presence of three clinical signs (ie, a restrictive pattern of lung impairment, a diffusion capacity below the lower limit of the normal range, and bilateral crackles at the posterior lung base in the latter part of or throughout the respiratory cycle); a history of relevant exposure; and, most important, chest radiographic findings that correspond to ILO classification s, t, or u parenchymal opacities (ie, small irregular opacities with a profusion of 1/1 or greater). Many physicians and epidemiologists have assessed chest radiographic findings in asbestos-exposed individuals according to the ILO classification system (2). However, some reports indicate that a reliance on chest radiography as the sole means of detecting asbestosis may be ill advised: Kipen et al (32) found that 18% of patients with biopsy-proved pulmonary fibrosis had no identifiable radiographic abnormalities and that 80% of patients had chest radiographic findings (according to the ILO classification) that did not correlate with the histopathologic grades.
There are no known radiographic findings that are pathognomonic of asbestosis. Initial chest radiographs show small irregular opacities with a fine reticular pattern, findings that represent peribronchiolar and adjacent alveolar interstitial fibrosis (Fig 14). In addition, pleural thickening or plaques may be seen.
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Figure 14. Asbestosis in a 58-year-old man who worked for 25 years in building construction. Chest radiograph shows small reticular opacities (arrows) at the costophrenic sulcus in the lower zone of both lungs.
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Thin-section CT scans may aid the differentiation of dependent atelectasis from irreversible fibrosis in the dorsal lung region with the depiction of changes indicative of lung fibrosis, especially septal thickening and parenchymal band formation (33). CT scans obtained in a prone position are important for distinguishing between normal increased opacity in the dependent lung regions and mild fibrosis (Fig 15). In the early stage of disease, minimal or no visible abnormalities may be observed on chest radiographs, although thin-section CT scans demonstrate thickened intralobular and interlobular lines, subpleural curvilinear lines, pleura-based irregular small nodules, hazy patches of increased attenuation, and small cystic spaces (34) (Fig 15). Honeycombing is a common finding in advanced-stage disease, predominantly in the lung periphery and the posterior region (35) (Fig 16). Thin-section CT findings in patients with interstitial fibrosis are similar to those in patients with idiopathic pulmonary fibrosis. However, in a comparative CT study of asbestosis and idiopathic pulmonary fibrosis (36), the distribution of fibrosis in the idiopathic pulmonary fibrosis group was more often basal and subpleural than that in the asbestosis group (Fig 16). The presence of parietal pleural thickening in association with lung fibrosis is the most important feature differentiating asbestos-induced pulmonary fibrosis from idiopathic pulmonary fibrosis; this finding is highly suggestive of asbestosis in patients with a history of asbestos exposure. Moreover, the presence of asbestos bodies in bronchoalveolar lavage fluid is highly specific (37).
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Figure 15a. Asbestosis in a 59-year-old man who worked for 30 years at an automobile factory. (a) Axial thin-section CT scan (1.5-mm-thick section) obtained at the level of the liver dome with the patient prone shows small subpleural nodules (straight arrows), patchy ground-glass opacities (curved arrows), and interlobular septal thickening (arrowhead) suggestive of early-stage asbestosis. (b) CT scan obtained with mediastinal window settings at the level of the suprahepatic inferior vena cava shows bandlike pleural thickening (arrowheads) in the lower lobe of both lungs, a finding indicative of pleural plaque. (c) Photomicrograph (original magnification, x12; hematoxylin-eosin stain) of a pathologic specimen obtained with video-assisted thoracoscopic surgical biopsy depicts subpleural and septal fibrous thickening (arrows).
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Figure 15b. Asbestosis in a 59-year-old man who worked for 30 years at an automobile factory. (a) Axial thin-section CT scan (1.5-mm-thick section) obtained at the level of the liver dome with the patient prone shows small subpleural nodules (straight arrows), patchy ground-glass opacities (curved arrows), and interlobular septal thickening (arrowhead) suggestive of early-stage asbestosis. (b) CT scan obtained with mediastinal window settings at the level of the suprahepatic inferior vena cava shows bandlike pleural thickening (arrowheads) in the lower lobe of both lungs, a finding indicative of pleural plaque. (c) Photomicrograph (original magnification, x12; hematoxylin-eosin stain) of a pathologic specimen obtained with video-assisted thoracoscopic surgical biopsy depicts subpleural and septal fibrous thickening (arrows).
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Figure 15c. Asbestosis in a 59-year-old man who worked for 30 years at an automobile factory. (a) Axial thin-section CT scan (1.5-mm-thick section) obtained at the level of the liver dome with the patient prone shows small subpleural nodules (straight arrows), patchy ground-glass opacities (curved arrows), and interlobular septal thickening (arrowhead) suggestive of early-stage asbestosis. (b) CT scan obtained with mediastinal window settings at the level of the suprahepatic inferior vena cava shows bandlike pleural thickening (arrowheads) in the lower lobe of both lungs, a finding indicative of pleural plaque. (c) Photomicrograph (original magnification, x12; hematoxylin-eosin stain) of a pathologic specimen obtained with video-assisted thoracoscopic surgical biopsy depicts subpleural and septal fibrous thickening (arrows).
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Figure 16a. Asbestosis in a 70-year-old man who worked for 30 years in a shipyard. (a, b) Axial thin-section CT scans (1.0-mm-thick sections) at the level of the suprahepatic inferior vena cava. (a) Scan obtained with lung window settings shows subpleural consolidation (arrow) in the lower lobe of the left lung, with reticulation, ground-glass opacities, and honeycombing. (b) Scan obtained with mediastinal window settings shows subpleural consolidation (arrow), pleural thickening (arrowheads) and effusion. (c, d) Photomicrographs of pathologic specimens obtained with video-assisted thoracic surgical biopsy. (c) Low-power micrograph (original magnification, x40; hematoxylin-eosin stain) shows dense collagen fibers in the pleura (arrows). (d) High-power micrograph (original magnification, x200; iron stain) shows asbestos bodies in the parenchyma (arrows).
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Figure 16b. Asbestosis in a 70-year-old man who worked for 30 years in a shipyard. (a, b) Axial thin-section CT scans (1.0-mm-thick sections) at the level of the suprahepatic inferior vena cava. (a) Scan obtained with lung window settings shows subpleural consolidation (arrow) in the lower lobe of the left lung, with reticulation, ground-glass opacities, and honeycombing. (b) Scan obtained with mediastinal window settings shows subpleural consolidation (arrow), pleural thickening (arrowheads) and effusion. (c, d) Photomicrographs of pathologic specimens obtained with video-assisted thoracic surgical biopsy. (c) Low-power micrograph (original magnification, x40; hematoxylin-eosin stain) shows dense collagen fibers in the pleura (arrows). (d) High-power micrograph (original magnification, x200; iron stain) shows asbestos bodies in the parenchyma (arrows).
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Figure 16c. Asbestosis in a 70-year-old man who worked for 30 years in a shipyard. (a, b) Axial thin-section CT scans (1.0-mm-thick sections) at the level of the suprahepatic inferior vena cava. (a) Scan obtained with lung window settings shows subpleural consolidation (arrow) in the lower lobe of the left lung, with reticulation, ground-glass opacities, and honeycombing. (b) Scan obtained with mediastinal window settings shows subpleural consolidation (arrow), pleural thickening (arrowheads) and effusion. (c, d) Photomicrographs of pathologic specimens obtained with video-assisted thoracic surgical biopsy. (c) Low-power micrograph (original magnification, x40; hematoxylin-eosin stain) shows dense collagen fibers in the pleura (arrows). (d) High-power micrograph (original magnification, x200; iron stain) shows asbestos bodies in the parenchyma (arrows).
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Figure 16d. Asbestosis in a 70-year-old man who worked for 30 years in a shipyard. (a, b) Axial thin-section CT scans (1.0-mm-thick sections) at the level of the suprahepatic inferior vena cava. (a) Scan obtained with lung window settings shows subpleural consolidation (arrow) in the lower lobe of the left lung, with reticulation, ground-glass opacities, and honeycombing. (b) Scan obtained with mediastinal window settings shows subpleural consolidation (arrow), pleural thickening (arrowheads) and effusion. (c, d) Photomicrographs of pathologic specimens obtained with video-assisted thoracic surgical biopsy. (c) Low-power micrograph (original magnification, x40; hematoxylin-eosin stain) shows dense collagen fibers in the pleura (arrows). (d) High-power micrograph (original magnification, x200; iron stain) shows asbestos bodies in the parenchyma (arrows).
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The two most important complications of asbestosis are pulmonary fibrosis and pleuropulmonary malignancy (3). The individual risk of death from asbestosis increases significantly with the increasing severity of underlying pulmonary fibrosis (38). With regard to pleuropulmonary malignancy, there is a period of latency of at least 20 years between the initial exposure to asbestos and the development of a pulmonary carcinoma or pleural mesothelioma (39). Apart from the potential pulmonary complications, various extrathoracic neoplasms also are reported to be associated with asbestos exposure, a group that includes peritoneal mesothelioma and gastrointestinal, renal, oropharyngeal, and laryngeal carcinoma, as well as leukemia (3).
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Berylliosis
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Berylliosis, a chronic granulomatous lung disease caused by exposure t
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Abstract
LEARNING OBJECTIVES FOR TEST...
