The crazy-paving pattern: A radiological-pathological correlated and illustrated overview

Transcription

1 The crazy-paving pattern: A radiological-pathological correlated and illustrated overview Poster No.: C-0827 Congress: ECR 2010 Type: Educational Exhibit Topic: Chest Authors: W. F. M. De Wever, J. Coolen, J. Meersschaert, E. Verbeken, J. Verschakelen; Leuven/BE Keywords: crazy-paving pattern, ground-glass opacification, linear pattern DOI: /ecr2010/C-0827 Any information contained in this pdf file is automatically generated from digital material submitted to EPOS by third parties in the form of scientific presentations. References to any names, marks, products, or services of third parties or hypertext links to thirdparty sites or information are provided solely as a convenience to you and do not in any way constitute or imply ECR's endorsement, sponsorship or recommendation of the third party, information, product or service. ECR is not responsible for the content of these pages and does not make any representations regarding the content or accuracy of material in this file. As per copyright regulations, any unauthorised use of the material or parts thereof as well as commercial reproduction or multiple distribution by any traditional or electronically based reproduction/publication method ist strictly prohibited. You agree to defend, indemnify, and hold ECR harmless from and against any and all claims, damages, costs, and expenses, including attorneys' fees, arising from or related to your use of these pages. Please note: Links to movies, ppt slideshows and any other multimedia files are not available in the pdf version of presentations. Page 1 of 43

2 Learning objectives To recognize a crazy-paving pattern. To understand how to explain the ground-glass opacification and the reticular pattern of a crazy-paving pattern. To make a differential diagnosis of crazy-paving pattern. Background Superposition of a linear pattern on ground-glass opacity results in a pattern that is termed crazy-paving. The crazy-paving pattern is a common finding at thin-section computed tomography (HRCT) but also on multidetector computed tomography (MDCT). Groundglass opacity is defined as a hazy increase in lung density with preservation of airway and vessel margins. Ground-glass opacity occurs when there is a mild decrease in the amount of air in the airspaces and a thickening of the alveolar wall and the interstitium. The linear component can be caused by a thickening of the interlobular septa (septal lines), a thickening of the intralobular septa and the intralobular interstitium (intralobular reticular pattern and intralobular branching lines) or a linear deposition of material within the airspaces at the borders of the acini (perilobular pattern) (fig. 1-5). The crazy-paving pattern was initially described as a pathognomonic sign of alveolar proteinosis, however nowadays; this pattern has been reported in a variety of acute and chronic diseases as summarized in fig.6. The purpose of this poster is to give a radiological-histopathological overview of different causes of crazy-paving pattern. Images for this section: Page 2 of 43

3 Fig. 1: Anatomy of the secondary pulmonary lobule Page 3 of 43

4 Fig. 2: The reticular pattern: thickening of the interlobular septa Page 4 of 43

5 Fig. 3: The reticular pattern: thickening of the intralobular interstitium Page 5 of 43

6 Fig. 4: The reticular pattern: irregular areas of fibrosis Page 6 of 43

7 Fig. 5: The reticular pattern: perilobular pattern Page 7 of 43

8 Fig. 6: Differential diagnosis of crazy-paving pattern Page 8 of 43

9 Imaging findings OR Procedure details Material and Methods We performed a retrospective review of the medical records in our radiological computed tomography database, ranging from 01/01/08 until 31/12/08 searching for patients reported with a "crazy paving" pattern on a CT of the chest. In total, 98 patients with a crazy-paving pattern were retained and reviewed. Most of the patients were scanned to rule out lung embolism, interstitial pathology or in an oncologic setting. All these patients underwent a dedicated MDCT of the chest with or without IV contrast, depending the reason of doing the chest CT. Only 7 patients with a crazy-paving pattern on chest CT underwent also a histopathological examination to make the definitive diagnosis. In 59 patients, the definitive diagnosis was made on a clinical base. In the remaining 32 patients, the cause of the crazy paving pattern was undecided. Results Ninety-eight patients with a crazy-paving pattern were retained and reviewed. Fig. 1 summarizes the different causes of the crazy-paving pattern as found on histopathological examination or based on clinical decision. Only seven patients underwent histopathological examination to establish the diagnosis. These seven patients will be discussed further in this poster. Patient 1 A 46-year-old man with progressive dyspnea since one week. He complained also of cough and the production of white mucus in the morning. He smoked one packet of cigarettes a day. Chest X-ray and chest CT were made. Chest X-ray (fig. 2) shows a reticular pattern most pronounced in the central parts of the lungs. There is also an increase in lung density central in both lungs. There are no arguments for pleural fluid and the heart and central vascular structures are normal. On CT, there is a patchy distribution of areas with increased lung attenuation. Superimposed on this increased lung attenuation a linear pattern is seen. These lines correspond with a deposition of material within the airspaces at the borders of the acini in the secondary pulmonary lobules (perilobular pattern) (fig. 3). Page 9 of 43

10 Histopathological evaluation of a specimen from open lung biopsy out of the right lung shows amorphous eosinophilic material in the alveoli, positive on periodic acid-schiff (PAS) staining. This eosinophilic material corresponds with deficient surfactant (fig. 4). The diagnosis of alveolar proteinosis was made. Patient 2 A 62-year-old woman with progressive shortness of breath on exercise. Chest X-ray and chest CT were made. Chest X-ray shows a patchy distribution of areas with increased lung density (fig. 6). There is also an increase of the linear pattern in both lungs. On CT, a crazy-paving pattern is seen with a geographic distribution of groundglass opacities with the superposition of thickened inter- and intralobular septa. The findings are seen predominantly in the upper lung areas (fig. 7). Although the patient had no history of bird exposure, serum precipitins against pigeons were elevated. To resolve this paradox, an open long biopsy was performed. Histology demonstrates an interstitial pneumonia with lymphocytes, plasma cells and foamy macrophages in the interstitium. Epitheloid granulomas without caseation are also seen. There is no fibrosis. (fig. 8) The diagnosis of hypersensitivity pneumonitis was made. Patient 3 An 80-year-old man with a rapidly progressive dyspnea. Chest X-ray and chest CT were made. Chest X-ray shows patchy distribution of areas with consolidation and ground-glass opacity. There is also a fine reticular pattern, most pronounced in the periphery of both lungs (fig. 10). Chest CT which was performed to rule out lung embolism could not demonstrate lung emboli. A crazy-paving pattern was visible with a scattered distribution of areas with ground-glass opacification. Superimposed on this increased lung attenuation a linear pattern with multiple small irregular lines is visible. Tractionbronchiectasis are seen in the periphery of both lungs (fig. 11). On histology, thickening of the interstitium with variable degree of severity is seen, leaving some alveolar septa almost completely normal whereas others show thickening. Fibrinous exsudates, honeycombing and mild inflammatory alveolitis are also present (fig. 12). The diagnosis of Usual Interstitial Pneumonia (UIP) was made. Page 10 of 43

11 Patient 4 A 56-year-old woman, with increasing dyspnea. Chest X-ray and chest CT were made. Chest X-ray shows a reticulation of the lung parenchyma, diffusely spread in both lungs, central and peripheral (fig. 14). Chest CT showed a crazy-paving pattern especially in the periphery of both lungs. There is an increase of lung attenuation (ground-glass opacification). There is a superposition of a reticular pattern with thickening of the inter- and intralobular septa (fig. 15). Histological evaluation shows a homogeneous fibrotic thickening of the interstitium with inflammation. Macrophages are visible within the alveolar septa (fig. 16). The diagnosis of Non Specific Interstitial Pneumonia (NSIP) was made. Patient 5 A 71-year-old man with a limited small cell lung cancer; developed fever and cough, after radiation therapy. Chest X-ray and chest CT were made. Chest X-ray shows an area of consolidation in the right lung with airbronchogram. There is also loss of volume of the right lung (fig. 18). CT shows therapy response on the tumor. There is a patchy distribution of a crazypaving pattern with increased lung attenuation (ground-glass opacity) and thickening of the interlobular en intralobular septa (fig. 19). Histologic examination after autopsy shows airspace filling with an exsudate in combination with thickening of the interlobular septa, thickening of the interstitium surrounding the airspaces, and also the presence of irregular fibrosis (fig. 20). The diagnosis of radiation pneumonitis was made. Patient 6 A 54-year-old man with progressive dyspnea. Chest X-ray and chest CT were made. Chest X-ray shows consolidation in the caudal region of the right lung with airbronchogram. There are no signs of interstitial lung disease on chest X-ray (fig 22). Chest CT shows a crazy-paving pattern with areas of increased lung attenuation and with thickening of the interlobular septa even as thickening of the intralobular interstitium in the right middle and lower lobe (fig. 23). Page 11 of 43

12 Histological examination shows alveoli filled with lipid particles, some of them ingested in macrophages with the formation of lipid granulomas (fig.24). The diagnosis of exogeneous lipid pneumonia was made. Patient 7 A 73-year-old woman with an insidious onset of unexplained and progressive dyspnea. Chest X-ray and chest CT were made. Chest X-ray shows a pleural effusion in the right hemithorax. An increased reticular pattern is seen in the left upper lung field and in a lesser degree also in the right upper lung field (fig. 26). CT scan shows a diffuse crazypaving pattern with areas of ground-glass attenuation and thickening of interlobular septa. There are also some small nodular lesions visible mostly in the left upper lobe suggestive for pulmonary metastases (fig. 27). Histological examination of autopsy specimen demonstrates thickening of the interlobular septa due to fibrosis and the presence of tumor cells. There is also perivascular thickening due to an expansion of lymphatic spaces by tumor cells (fig. 28). The diagnosis of lymphangitic carcinomatosis was made. Discussion The crazy-paving pattern is a nonspecific pattern. Initially, this pattern has been considered to be highly suggestive of alveolar proteinosis. Nowadays, we can find this pattern in different diseases: airspace diseases and interstitial diseases. The crazy-paving pattern consists of scattered or diffuse ground-glass attenuation with superposition of a linear pattern. These lines can be: thickened interlobular septa (septal lines), thickened intralobular septa and thickening of the intralobular interstitium (intralobular reticular pattern and intralobular branching lines) or it can be a linear deposition of material within the airspaces at the borders of the acini and the secondary pulmonary lobules (perilobular pattern). Alveolar proteinosis (patient 1) and exogeneous lipoid pneumonia (patient 6) are airspace diseases. In alveolar proteinosis, airspaces are filled with a phospholipoproteinaceous material. On CT, the filling of the alveoli is responsible for the ground-glass appearance. When the airspaces adjacent to the inter- and intralobular septa and to the alveolar walls fill, the perilobular pattern becomes visible (fig. 5). Page 12 of 43

13 Exogeneous lipid pneumonia is the result of chronic inhalation of oily substances and is primarily a disease that affects the alveolar spaces. On CT, diffuse ground-glass opacities and consolidations, sometimes with fat attenuation caused by large lipid particles and numerous lipid-laden macrophages distending the alveolar spaces can be seen, especially in the lower lung areas (fig. 25). Hypersensitivity pneumonitis (patient 2), UIP (patient 3), NSIP (patient 4), radiation pneumonitis (patient 5) and lymphangitic spread of carcinoma (patient 7) are interstitial diseases. In hypersensitivity pneumonitis, antigen-antibody complexes around the microvasculature cause a neutrophil-rich inflammatory response and subsequent tissue injury. Biopsy in the subacute phase shows heavy infiltrates of lymphocytes and plasma cells in the walls of the alveoli in combination with poorly formed granulomas containing foreign body giant cells. In chronic phases, the interstitial inflammation remains but fibrosis becomes more apparent and honeycombing can occur. On CT, the alterations in the walls of the alveoli and the inflammation in the interstitium are visible as thickening of the inter- and intralobular lines and thickening of the intralobular interstitium (fig. 9). Interstitial pulmonary fibrosis is characterized by ground-glass opacities, traction bronchiectasis, and subpleural reticular opacities and honeycombing, increasing from the apex to the base. On histology, the hallmark is a geographically and temporally heterogeneous parenchymal fibrosis against a background of continuing mild inflammation (fig. 13). In NSIP the predominant finding on HRCT is subpleural, patchy, ground-glass opacification, predominantly in the basal lung zones. Traction bronchiectasies, subpleural microcystic honeycombing and irregular linear opacities can be seen in more advanced cases. On histology, a homogeneous interstitial inflammation is seen, corresponding to the diffuse ground-glass opacities whereas fibrosis in the interstitium is related to the superimposed linear pattern (fig. 17). The inflammation of lung tissue, secondary to radiation therapy, is situated in the tissue within the radiation field and depends on the interval of completion of treatment. In the acute phase (4 to 12 weeks after completion of radiation therapy), the histologic reaction is that of diffuse alveolar damage and consists of hyaline membranes in the alveolar ducts and respiratory bronchioles while the alveolar spaces fill with an exudate of proteinaceous material. This corresponds to the ground-glass opacities typically manifesting on CT. The reticular pattern that can be seen in this phase is due to congestion of capillaries and edema of the interstitium (fig. 21). Page 13 of 43

14 Pulmonary lymphangitic carcinomatosis is a metastatic lung disease characterized by diffuse spread of tumor to the pulmonary lymphatic system. When tumoral cells spread to the pulmonary lymphatic system and perilymphatic interstitial tissue; an interstitial thickening is seen on CT. The proliferation of these cells in combination with lymphatic dilatation contributes to this interstitial thickening (fig. 29). Images for this section: Fig. 1: Different causes of crazy-paving pattern in our database Page 14 of 43

15 Fig. 2: Chest X-ray shows a reticular pattern most pronounced in the central parts of the lungs. There is also a decrease of the lung translucency central in both lungs. Heart en central vessels are normal. There is no pleural effusion. Page 15 of 43

16 Fig. 3: On CT, there is a patchy distribution of a crazy-paving pattern. The lines correspond with a deposition of material within the airspaces at the borders of the acini (1) in the secondary pulmonary lobules, but also along the interlobular (2) and intralobular septa (3): the perilobular pattern. Page 16 of 43

17 Fig. 4: Histopathological evaluation of a specimen out of the right lung shows amorphous eosinophilic material in the alveoli (*) positive on periodic acid-schiff (PAS) staining. This material corresponds with deficient surfactant. Page 17 of 43

18 Fig. 5: Radiological-histopathological correlation. Filling of the alveoli (*) is responsible for the ground-glass appearance on CT. When the airspaces adjacent to the interand intralobular septa (black arrow) and to the alveolar walls fill, the perilobular pattern becomes visible. Page 18 of 43

19 Fig. 6: Chest X-ray shows a patchy distribution of areas with increased lung density. There is also an increase of the linear pattern in both lungs. Page 19 of 43

20 Fig. 7: On CT, a crazy-paving pattern is seen with a geographic distribution of groundglass opacities with the superposition of thickened inter- (1) and intralobular (2) septa. The findings are seen predominantly in the upper lung areas. Page 20 of 43

21 Fig. 8: Histology demonstrates an interstitial pneumonia with lymphocytes, plasma cells and foamy macrophages in the interstitium. Epitheloid granulomas without caseation are also seen. There is no fibrosis. Page 21 of 43

22 Fig. 9: Radiological-histopathological correlation. The alterations in the walls of the alveoli and the inflammation in the interstitium are visible as thickening of the inter- and intralobular lines. Page 22 of 43

23 Fig. 10: Chest X-ray shows patchy distribution of areas with consolidation and groundglass opacity. There is also a fine reticular pattern, most pronounced in the periphery of both lungs. Page 23 of 43

24 Fig. 11: A crazy-paving pattern is visible with a scattered distribution of areas with groundglass opacification. Superimposed on this increased lung attenuation a linear pattern with multiple small irregular lines is visible (intralobular fibrosis) (1). Tractionbronchiectasis are seen in the periphery of both lungs (white arrow). Page 24 of 43

25 Fig. 12: On histology, thickening of the interstitium (arrow) with variable severity is seen, leaving some alveolar septa almost completely normal whereas others show thickening. Fibrinous exsudates, honeycombing (*) and mild inflammatory alveolitis are also present. Page 25 of 43

26 Fig. 13: Radiological-histopathological correlation. On histology, the hallmark of UIP is a geographically and temporally heterogeneous parenchymal fibrosis against a background of continuing mild inflammation corresponding with intralobular fibrosis en honeycombing on CT. Page 26 of 43

27 Fig. 14: Chest X-ray shows a reticulation in the lung parenchyma, diffusely spread in both lungs, central en peripheral. Page 27 of 43

28 Fig. 15: Chest CT shows a crazy-paving pattern especially in the periphery of both lungs. There is an increase of lung attenuation (ground-glass opacification). There is a superposition of a reticular pattern with thickening of the inter- (1) and intralobular (2) septa. Page 28 of 43

29 Fig. 16: Histological evaluation shows a homogeneous fibrotic thickening of the interstitium with inflammation. Macrophages are visible within the alveolar septa. Page 29 of 43

30 Fig. 17: Radiological-histopathological correlation. Alveolar spaces filled with an exudate of proteinaceous material responsible for the ground-glass opacities on CT. The reticular pattern is due to congestion of capillaries and edema of the interstitium. Page 30 of 43

31 Fig. 18: Chest X-ray shows an area of consolidation in the right lung with airbronchogram. There is also loss of volume of the right lung. Page 31 of 43

32 Fig. 19: CT showed therapy response on the tumor. There is a patchy distribution of a crazy-paving pattern with increased lung attenuation (ground-glass opacity) and thickening of the interlobular septa (1). Page 32 of 43

33 Fig. 20: Histologic examination after autopsy showed airspace filling with an exsudate in combination with thickening of the interlobular septa (arrow), thickening of the interstitium surrounding the airspaces, and also the presence of irregular fibrosis (white arrow). Page 33 of 43

34 Fig. 21: Radiological-histopathological correlation. Alveolar spaces filled with an exudate of proteinaceous material responsible for the ground-glass opacities on CT. The reticular pattern is due to congestion of capillaries and edema of the interstitium. Page 34 of 43

35 Fig. 22: Chest X-ray shows consolidation in the caudal region of the right lung with airbronchogram. Page 35 of 43

36 Fig. 23: Chest CT shows a crazy-paving pattern with areas of increased lung attenuation and with thickening of interlobular septa (1) even as thickening of the intralobular interstitium (2). Page 36 of 43

37 Fig. 24: Histological examination shows alveoli filled with lipid particles (*), some ingested in macrophages (+) with the formation of lipid granulomas. Page 37 of 43

38 Fig. 25: Radiological-histopathological correlation. Page 38 of 43

39 Fig. 26: Chest X-ray shows a pleural effusion in the right hemithorax. An increased linear pattern is seen in the left and right upper lung. Page 39 of 43

40 Fig. 27: CT scan shows a diffuse crazy paving pattern with areas of ground-glass attenuation and thickening of interlobular septa (1). There are also some small nodular lesions visible mostly in the left upper lobe suggestive for pulmonary metastases (2). Page 40 of 43

41 Fig. 28: Histological examination of autopsy specimen demonstrats thickening of the interlobular septa (*) due to fibrosis and the presence of tumor cells. There is also perivascular (arrow) thickening due to an expansion of lymphatic spaces by tumor cells. Page 41 of 43

42 Fig. 29: Radiological-histopathological correlation. The histologic reaction is that of diffuse alveolar damage and consists of hyaline membranes in the alveolar ducts and respiratory bronchioles while the alveolar spaces fill with an exudate of proteinaceous material. This corresponds to the ground-glass opacities on CT. The reticular pattern is due to congestion of capillaries and edema of the interstitium. Page 42 of 43

43 Conclusion The crazy-paving pattern on CT is a nonspecific finding. It is characterized by scattered or diffuse ground-glass attenuation with superposition of a linear pattern. This linear network can be caused by thickening of interlobular or intralobular septa or the presence of intralobular fibrosis or it can be caused by a linear deposition of material within the airspaces. Although the crazy-paving pattern is nonspecific, the various diseases that can cause this appearance can often be distinguished by their clinical findings and other additional findings on CT. Personal Information prof. dr. Walter De Wever thoraxradioloog - chest radiologist walter.dewever@uz.kuleuven.ac.be tel: fax: UZ Leuven campus Gasthuisberg Herestraat 49 B Leuven References 1. Frazier AA, Franks TJ, Cooke EO, Mohammed TL, Pugatch RD, Galvin JR. From the archives of the AFIP: pulmonary alveolar proteinosis. Radiographics 2008: 28(3): ; quiz Johkoh T, Itoh H, Muller NL, Ichikado K, Nakamura H, Ikezoe J, Akira M, Nagareda T. Crazy-paving appearance at thin-section CT: spectrum of disease and pathologic findings. Radiology 1999: 211(1): Rossi SE, Erasmus JJ, Volpacchio M, Franquet T, Castiglioni T, McAdams HP. "Crazy-paving" pattern at thin-section CT of the lungs: radiologic-pathologic overview. Radiographics 2003: 23(6): Page 43 of 43