- Email: [email protected]
Computed tomography findings in 66 patients with malignant pleural mesothelioma due to environmental exposure to asbestos
Clinical Imaging 30 (2006) 177 – 180
Computed tomography findings in 66 patients with malignant pleural mesothelioma due to environmental exposure to asbestos ¨ nala, AyYenaz O ¨ ktena, Deniz Kfksala,4, Mine O ¨ zcana, Cebrail XimYeka, Hakan Ertqrkb Fethiye O a
Department of Chest Diseases, Atatu¨rk Chest Diseases and Chest Surgery Education and Research Hospital, 06280 Ankara, Turkey b Department of Radiology, Atatu¨rk Chest Diseases and Chest Surgery Education and Research Hospital, 06280 Ankara, Turkey Received 5 October 2005; accepted 28 December 2005
Abstract We aimed to investigate the computed tomography (CT) findings of malignant pleural mesothelioma (MPM) caused by environmental asbestos exposure. We retrospectively reviewed CT scans of 66 patients, which were performed before any invasive procedure was done. Pleural effusion (80.3%), pleural thickening (77.2%), volume contraction (37.9%), involvement of mediastinal pleura (31.8%) and interlobar fissure (28.8%) were the most common CT findings of MPM. Although none of these findings are pathognomonic for MPM, they may provide valuable clues for the differential diagnosis, at least in patients with a history of asbestos exposure. D 2006 Elsevier Inc. All rights reserved. Keywords: Computed tomography; Environmental asbestos exposure; Malignant pleural mesothelioma
1. Introduction Malignant pleural mesothelioma (MPM) is primary tumor of mesodermal origin, which is almost exclusively due to inhalation of asbestos fibers [1,2]. While it is due to occupational exposure in European countries, it is due to environmental exposure in Turkey. It is an important health problem in Turkey due to many asbestos deposits, which exist in some rural parts of central and eastern Anatolia [3–5]. Asbestos containing soil is used as whitewash or plaster material, as a substitute for baby powder, and on roofs for insulation and prevention of water leakage. One of the most important routes of domestic exposure is from dust originating from the walls of homes that have been whitewashed with white stucco every year. Consequently, householders are repeatedly exposed to asbestos fibers at an early age [3,4]. Erionite, a naturally occurring fibrous zeolite crystal that is found in volcanic tuffs of the Cappadocia region of central Anatolia, is also associated with MPM [6– 9]. The diagnosis of MPM is often delayed either because the symptoms are nonspecific or because MPM is relatively rarely diagnosed by pleural fluid cytology and/or closed
4 Corresponding author. Feneryolu sok. 5/21, 06010 Etlik, Ankara, Turkey. Tel.: +90 312 321 29 04; fax: +90 312 355 21 35. E-mail address: [email protected] (D. Kfksal). 0899-7071/06/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.clinimag.2005.12.027
pleural biopsy alone [10]. Cytologic diagnosis of MPM from pleural fluid alone is unreliable since reactive mesothelial cells and cells from other malignant tumors such as sarcomas and adenocarcinomas are often very difficult to distinguish from malignant mesothelial cells [11]. Therefore, histologic assessment is preferred. Sometimes a biopsy procedure that can be performed blindly, under computed tomography (CT) or ultrasonography guidance, or thoracoscopically may be insufficient to provide the diagnosis. In such a circumstance, CT may contribute to the diagnosis noninvasively, although non of the findings are pathognomonic for MPM [12,13]. In this study, we aimed to investigate the CT findings of 66 patients with MPM caused by environmental exposure to asbestos fibers. 2. Materials and methods Computed tomography scans of 66 patients who were diagnosed as MPM in our clinic during a 7-year period (1998–2004) were retrospectively reviewed. None of the patients had occupational exposure to asbestos, but all of them had a history of environmental exposure to asbestos. The CT scans were performed before any invasive procedure was done. Evaluation was carried out in chest images obtained in 10-mm-thick slices from the apices of the lungs to costophrenic angles. All the sections were taken in
F. O¨kten et al. / Clinical Imaging 30 (2006) 177–180
178
Table 1 The diagnostic methods and histologic subtypes of the patients Diagnostic method Closed pleural biopsy Thoracoscopy Thoracotomy CT-guided biopsy Histologic subtype Epithelial Sarcomatous Mixed Indifferentiated
3. Results
n
%
55 6 2 3
83.4 9.1 3 4.5
12 2 4 48
18.2 3 6 72.8
the supine position at the end of inspiration. Both mediastinal and parenchymal window settings were used. Intravenous iodinated contrast medium was used to determine mediastinal lymph node enlargement and/or the relation of lesions to adjacent vascular structures. The CT scans were evaluated by a study group including three chest physicians and a radiologist. A conclusion was reached by consensus. Pleural effusion was classified as unilateral and bilateral and massive and moderate. Massive pleural effusion was defined as the effusion occupying more than half of the hemithorax. Pleural thickening was classified as diffuse, nodular, and mass lesion. Diffuse pleural thickening was defined as a diffuse pleural thickness V 10 mm. Nodular pleural thickening was defined as focal pleural thickening between 10 and 30 mm. Pleura-based soft tissue mass with a width of z 30 mm or more was defined as mass lesion. Transversal or craniocaudal pleural thickening b 50 mm in length was defined as pleural plaque. Involvement of mediastinal pleura is defined as pleural thickening bordering the mediastinum. Involvement of interlobar fissures was defined as thickening of the pleural surfaces of the interlobar fissure. Mediastinal shift was defined as dislocation of the mediastinal structures due to pleural lesions. Volume contraction was defined as contraction of the involved hemithorax or mediastinal displacement, distortion of bronchovascular structures, elevation of ipsilateral hemidiaphragm, and compansatory hyperinflation of contralateral lung. Mediastinal lymph nodes were considered as pathologically enlarged when their short-axis diameter was longer than 10 mm in the transverse plane. Supplementary radiological findings such as involvement of pericardium, diaphragmatic pleura, chest wall, lung parenchyma, pneumothorax, and calcified pleural plaques were also noted. Statistical analysis was carried out using SPSS programme version 12.0 (SPSS Chicago IL, USA). Descriptive statistical tests were used for analysis of data. Mann-Whitney U test was used to compare differences in means of continuous variables. Any P value V .05 was considered to be statistically significant.
Forty-five male patients with a mean age of 56.8F 10.7 years (range: 30 –76), and 21 female patients with a mean age of 56.9F14.8 years (range: 35 –84) were included in the study. The mean age of all the patients was 56.8F 12.1 years (range: 30 –84). Male/female ratio was 2.1/1. There was not any significant difference between the mean ages of male and female patients ( P =.9). The overall mean age of 66 patients was 56.8F12.1 years (range: 30– 84). Nine patients (13.6%) were 40 years old or younger. The methods of diagnosis and histologic subtypes of the patients are presented in Table 1. The diagnosis of MPM was confirmed by histopathologic examination of pleural tissue samples obtained by closed pleural biopsy in 55 (83.4%), thoracoscopy in 6 (9.1%), thoracotomy in 2 (3%), and CT-guided percutaneous biopsy in 3 (4.5%) patients. The histologic subtypes were epithelial in 12 (18.2%), sarcomatous in 2 (3%), mixed in 4 (6%), and indifferentiated in 48 (72.8%) patients. The CT findings of the patients with MPM are listed in Table 2. Right hemithorax was affected more frequently (56.1%) than left hemithorax (42.4%). Bilateral involvement was found in only one (1.5%) patient. The most common CT finding was pleural effusion, which was present in 80.3% (n = 53) of the patients. The effusion was massive in 22 (41.5%) and moderate in 31 (58.5%) patients. The mediastinum was displaced to the contralateral side in eight patients (15%). Pleural thickening was present in 77.2% (n =51) of the patients. Pleural thickening was diffuse in
Table 2 CT findings of 66 patients with MPM Patients Radiological findings
n
%
Hemithorax involvement Right hemithorax Left hemithorax Bilateral hemithorax Pleural effusion Unilateral/bilateral Massive/moderate Pleural thickening Diffuse Nodular Mass lesion Calcified pleural plaques Involvement of mediastinal pleura Involvement of diaphragmatic pleura Involvement of interlobar fissures Involvement of lung parenchyma Volume contraction Mediastinal shift Lymphadenopathy Pericardial involvement Chest wall invasion Pneumothorax
37 28 1 53 52/1 22/31 51 9 31 11 8 21 4 19 4 25 8 6 4 6 2
56.1 42.4 1.5 80.3 98.1/1.9 41.5/58.5 77.2 17.6 60.8 21.6 12.1 31.8 6.1 28.8 6.1 37.9 12.1 9.1 6.1 9.1 3
F. O¨kten et al. / Clinical Imaging 30 (2006) 177–180
Fig. 1. Circumferential pleural thickening with mediastinal pleural involvement (A) and interlobar fissure involvement (B) in a patient with MPM.
17.6% (n = 9), nodular in 60.8% (n = 31), and mass type in 21.6% (n = 11) of these patients. The other CT findings were volume contraction in 25 (37.9%), mediastinal pleural involvement in 21 (31.8%), interlobar fissure involvement in 19 (28.8%), mediastinal shift in eight (12.1%), calcified pleural plaques in eight (12.1%), chest wall invasion in six (9.1%), lympadenopathy in six (9.1%), diaphragmatic pleural involvement in four (6.1%), lung parenchyma involvement in four (6.1%) patients, pericardial involvement in four (6.1%), and pneumothorax in two (3%) patients. Circumferential pleural thickening with mediastinal pleural involvement (Fig. 1A) and interlobar fissure involvement (Fig. 1B) are demonstrated in a patient with MPM in Fig. 1. 4. Discussion In the present study, we retrospectively reviewed the CT scans of 66 patients with MPM. The evaluation of CT scans demonstrated that pleural effusion, pleural thickening, volume contraction, involvement of mediastinal pleura, and interlobar fissure were the most common CT findings. Since the diagnosis of MPM was confirmed by histopathologic examination of pleural tissue samples obtained by
179
closed pleural biopsies in most of the cases (83.4%), the histologic subtypes were indifferentiated in 72.8% of the cases. Relatively small biopsies obtained by blinded closed pleural biopsy were not adequate for differentiating histologic subtypes. Therefore, we could not compare the CT findings of histologic subtypes. It is known that the latency period between initial exposure to asbestos and the development of MPM is long and averages 30 – 40 years [14] with a range as great as 14 – 72 years [15]. MPM due to previous occupational exposure to asbestos is usually diagnosed in the fifth to seventh decades of life, with a mean age of approximately 60 years [16]. Due to the early age at the onset of exposure, the mean ages of MPM patients with environmental asbestos exposure are lower. In the present study, the mean age was 56 years and a high ratio (13.6%) of the patients were 40 years old or younger. The youngest patient was 30 years old. A strong male predominance is present when occupational exposure to asbestos is involved. In the present study, there was not any occupational exposure to asbestos, but still, there was also a slight male predominance. This can be explained by the more frequent use of hospital services by the male population compared to females in rural parts of Turkey. CT is an accurate and reliable radiographic technique in diagnosing and determining the extent of mesothelioma. It can represent a significant improvement over chest radiography, although its sensitivity and specificity for predicting the malignant nature of diffuse pleural lesions based upon morphologic criteria are only 72% and 83%, respectively [12]. Furthermore, CT lacks sensitivity for detecting miliary pleural seeding and critical invasion into the mediastinum or through the diaphragm [17]. Although it is not pathognomonic, the most characteristic feature of MPM is the presence of extensive, lobular, thickened irregular pleural masses that involved all pleural surfaces including the mediastinum [18]. In the present study, CT findings revealed a slight rightsided predominance (56.1%) of involvement by MPM, which is compatible with the literature [19]. Pleural effusion was the most common finding and was present in 80.3% of the cases. Although it is not a specific finding for MPM, it is reported to be present in 72–100% of the cases in the literature [10,13,17,20]. In this study, pleural effusion was the only finding without any pleural lesion in four cases (6.1%). In the study of Xenyig˘it et al. [13], 3% of cases presented with pleural effusion without pleural thickening or pleural plaques. Yilmaz et al [4] detected isolated pleural effusion in 2.2% of the patients with MPM. Based on these findings, a possible diagnosis of MPM must not be excluded in the absence of pleural thickening. Although it is rare, MPM must be considered in the differential diagnosis of pleural effusion and a history of exposure to asbestos. Pleural thickening was the second most common CT finding, which was present in 77.2% of the patients. It was mostly nodular (60.8%) in nature. Diffuse pleural thickening
180
F. O¨kten et al. / Clinical Imaging 30 (2006) 177–180
can be a manifestation of benign asbestos exposure, but when nodular thickening was present, it is difficult to distinguish it from MPM [21]. Leung et al [12] also reported that nodular pleural thickening was present in 63% of their MPM cases. Pleural plaques are the most common radiological manifestations of asbestos exposure. The presence of calcification suggests a benign process [12,18,22]. Although calcified plaques may be seen in MPM cases, they are uncommon [18]. In this study, calcified pleural plaques were present in eight patients (12.1%). Therefore, MPM must be considered in the differential diagnosis of calcified pleural plaques, especially when there is accompanying pleural effusion [3]. Irregular or nodular interlobar fissure involvement can be an early finding of MPM detected by CT. Free or localized pleural effusion and pleural thickening resulting from fibrosis can also involve the interlobar fissures. These were reported to cause smooth thickening of the fissures rather than the irregular or nodular thickening produced by MPM [10]. Interlobar fissure involvement was reported to be present in 53– 86% of the cases [3,13,14,22]. In the present study, it was present in 28.8% of the cases. Volume contraction resulting from the involvement of pleura is a common finding of MPM. The fixation of the mediastinum and volume contraction at the involved site are suggested as diagnostic features of MPM, but they may also be present in some benign and malign diseases of the chest [22]. Several studies had reported volume contraction in 42–73% [5,12–14,22]. In the present study, it was present in 37.9% of the cases. Involvement of lung parenchyma can be as pleural-based nodular masses extending into the lung or round, sharply demarcated masses located within the lung [18]. In this study, we detected parenchymal involvement in four patients (6.1%), and all were pleural-based masses extending into the lung. Xenyig˘it et al [13] reported lung penetration in 10% of their patients. On CT scans, enlarged lymph nodes may be seen in up to 50% of patients [17]. In this study, they were present in 9.1% of the cases. The results of this study, together with several other studies, range in a wide interval. This can be a result of different study populations at different stages of their diseases. In conclusion, pleural effusion, pleural thickening, volume contraction, involvement of mediastinal pleura, and interlobar fissure were the most common CT findings of MPM. Although none of these findings are pathognomonic for MPM, they may provide valuable clues for the differential diagnosis, at least in patients with a history of asbestos exposure. References [1] Albelda SM, Sterman DH, Litzky LA. Malignant mesothelioma and other primary pleural tumors. In: Fishman AP, editor. Fishman’s pulmonary diseases and disorders. New York7 McGraw-Hill, 1988. pp. 1453 – 66.
[2] Hillerdal G. Mesothelioma: cases associated with nonoccupational and low dose exposures. Occup Environ Med 1999;56:505 – 13. [3] Selc¸uk ZT, C ¸ fplq L, Emri S, Kalyoncu AF, Xahin AA, BarVY YI. Malignant pleural mesothelioma due to environmental mineral fiber exposure in Turkey: analysis of 135 cases. Chest 1992;102:790 – 6. [4] YVlmaz UM, Utkaner G, YalnVz E, Kumcuog˘lu Z. Computed tomographic findings of environmental asbestos-related malignant pleural mesothelioma. Respirology 1998;3:33 – 8. [5] Xahin AA, C ¸ fplq L, Selc¸uk ZT, EryVlmaz M, Emri S, Akhan O, BarVY YI. Malignant pleural mesothelioma caused by environmental exposure to asbestos and erionite in rural Turkey: CT findings in 84 patients. AJR Am J Roentgenol 1993;161:533 – 7. ¨ zesmi M, Kerse I, O ¨ zer E, Kolacan B, [6] BarVY YI, Xahin AA, O Altinors M, Goktepeli A. An outbreak of pleural mesothelioma and ¨ rgqp in Anatolia. chronic fibrosing pleurisy in the village of Karain/U Thorax 1978;33:181 – 92. [7] Artvinli M, BarVY YI. Environmental fiber-induced pleuro-pulmonary diseases in an Anatolian village: an epidemiological study. Arch Environ Health 1982;37:177 – 81. [8] BarVY I, Simonato L, Artvinli M, Pooley F, Saracci R, Skidmore J, Wagner C. Epidemiological and environmental evidence of the health effects of exposure to erionite fibers: a four year study in the Cappadocian region of Turkey. Int J Cancer 1987;39:10 – 7. [9] MetintaY M, Hillerdal G, MetintaY S. Malignant mesothelioma due to environmental exposure to erionite: follow-up of a Turkish emigrant cohort. Eur Respir J 1999;13:523 – 6. [10] Adams VI, Unni KK, Muhm JR, Jett JR, Ilstrup DM, Bernatz PE. Diffuse malignant mesothelioma of pleura. Diagnosis and survival in 92 cases. Cancer 1986;58:1540 – 51. [11] Henderson DW, Shilkin KB, Whitaker D. Reactive mesothelial hyperplasia vs mesothelioma, including mesothelioma in situ: a brief review. Am J Clin Pathol 1998;110:397 – 404. [12] Leung AN, Mqller NL, Miller RR. CT in differential diagnosis of diffuse pleural disease. AJR Am J Roentgenol 1990;154:487 – 92. [13] Xenyig˘it A, Bayram H, Babayig˘it C, Topc¸u F, Nazarog˘lu H, Bilici A, Leblebici I˙H. Malignant pleural mesothelioma caused by environmental exposure to asbestos in the southeast of Turkey: CT findings in 117 patients. Respiration 2000;67:615 – 22. [14] Erzen C, EryVlmaz M, Kalyoncu F, Bilir N, Xahin A, BarVY YI. CT findings in malignant pleural mesothelioma related to nonoccupational exposure to asbestos and fibrous zeolite (erionite). J Comput Assist Tomogr 1991;15:256 – 60. [15] Bianchi C, Giarelli L, Grandi G, Brollo A, Ramani L, Zuch C. Latency periods in asbestos-related mesothelioma of the pleura. Eur J Cancer Prev 1997;6:162 – 6. [16] Boutin C, Schlesser M, Frenay C, Astoul Ph. Malignant pleural mesothelioma. Eur Respir J 1998;12:972 – 81. [17] Rusch VW, Godwin JD, Shuman WP. The role of computed tomography scanning in the initial assessment and follow-up of the malignant pleural mesothelioma. J Thorac Cardiovasc Surg 1988;96: 171 – 7. [18] Rabinowitz JG, Efremidis SC, Cohen B, Dan S, Efremidis A, Chahinian AP, Teirstein AS. A comparative study of mesothelioma and asbestosis using computed tomography and conventional chest radiography. Radiology 1982;144:453 – 60. [19] Pistolesi M, Rusthoven J. Malignant pleural mesothelioma. Update, current management, and newer therapeutic strategies. Chest 2004; 126:1318 – 29. [20] YazVcVog˘lu S, ˙Ilc¸ayto R, BalcV K, SaylV BS, Yorulmaz B. Pleural calcification, pleural mesotheliomas, and bronchial cancers caused by tremolite dust. Thorax 1980;35:564 – 9. [21] Miller WT, Gefter WB, Miller WT. Asbestos-related chest diseases: plain radiographic findings. Semin Roentgenol 1992;27: 102 – 20. [22] Kawashima A, Libshitz HI. Malignant pleural mesothelioma: CT manifestations in 50 cases. AJR Am J Roentgenol 1990;155: 965 – 9.
Computed tomography findings in 66 patients with malignant pleural mesothelioma due to environmental exposure to asbestos ¨ nala, AyYenaz O ¨ ktena, Deniz Kfksala,4, Mine O ¨ zcana, Cebrail XimYeka, Hakan Ertqrkb Fethiye O a
Department of Chest Diseases, Atatu¨rk Chest Diseases and Chest Surgery Education and Research Hospital, 06280 Ankara, Turkey b Department of Radiology, Atatu¨rk Chest Diseases and Chest Surgery Education and Research Hospital, 06280 Ankara, Turkey Received 5 October 2005; accepted 28 December 2005
Abstract We aimed to investigate the computed tomography (CT) findings of malignant pleural mesothelioma (MPM) caused by environmental asbestos exposure. We retrospectively reviewed CT scans of 66 patients, which were performed before any invasive procedure was done. Pleural effusion (80.3%), pleural thickening (77.2%), volume contraction (37.9%), involvement of mediastinal pleura (31.8%) and interlobar fissure (28.8%) were the most common CT findings of MPM. Although none of these findings are pathognomonic for MPM, they may provide valuable clues for the differential diagnosis, at least in patients with a history of asbestos exposure. D 2006 Elsevier Inc. All rights reserved. Keywords: Computed tomography; Environmental asbestos exposure; Malignant pleural mesothelioma
1. Introduction Malignant pleural mesothelioma (MPM) is primary tumor of mesodermal origin, which is almost exclusively due to inhalation of asbestos fibers [1,2]. While it is due to occupational exposure in European countries, it is due to environmental exposure in Turkey. It is an important health problem in Turkey due to many asbestos deposits, which exist in some rural parts of central and eastern Anatolia [3–5]. Asbestos containing soil is used as whitewash or plaster material, as a substitute for baby powder, and on roofs for insulation and prevention of water leakage. One of the most important routes of domestic exposure is from dust originating from the walls of homes that have been whitewashed with white stucco every year. Consequently, householders are repeatedly exposed to asbestos fibers at an early age [3,4]. Erionite, a naturally occurring fibrous zeolite crystal that is found in volcanic tuffs of the Cappadocia region of central Anatolia, is also associated with MPM [6– 9]. The diagnosis of MPM is often delayed either because the symptoms are nonspecific or because MPM is relatively rarely diagnosed by pleural fluid cytology and/or closed
4 Corresponding author. Feneryolu sok. 5/21, 06010 Etlik, Ankara, Turkey. Tel.: +90 312 321 29 04; fax: +90 312 355 21 35. E-mail address: [email protected] (D. Kfksal). 0899-7071/06/$ – see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.clinimag.2005.12.027
pleural biopsy alone [10]. Cytologic diagnosis of MPM from pleural fluid alone is unreliable since reactive mesothelial cells and cells from other malignant tumors such as sarcomas and adenocarcinomas are often very difficult to distinguish from malignant mesothelial cells [11]. Therefore, histologic assessment is preferred. Sometimes a biopsy procedure that can be performed blindly, under computed tomography (CT) or ultrasonography guidance, or thoracoscopically may be insufficient to provide the diagnosis. In such a circumstance, CT may contribute to the diagnosis noninvasively, although non of the findings are pathognomonic for MPM [12,13]. In this study, we aimed to investigate the CT findings of 66 patients with MPM caused by environmental exposure to asbestos fibers. 2. Materials and methods Computed tomography scans of 66 patients who were diagnosed as MPM in our clinic during a 7-year period (1998–2004) were retrospectively reviewed. None of the patients had occupational exposure to asbestos, but all of them had a history of environmental exposure to asbestos. The CT scans were performed before any invasive procedure was done. Evaluation was carried out in chest images obtained in 10-mm-thick slices from the apices of the lungs to costophrenic angles. All the sections were taken in
F. O¨kten et al. / Clinical Imaging 30 (2006) 177–180
178
Table 1 The diagnostic methods and histologic subtypes of the patients Diagnostic method Closed pleural biopsy Thoracoscopy Thoracotomy CT-guided biopsy Histologic subtype Epithelial Sarcomatous Mixed Indifferentiated
3. Results
n
%
55 6 2 3
83.4 9.1 3 4.5
12 2 4 48
18.2 3 6 72.8
the supine position at the end of inspiration. Both mediastinal and parenchymal window settings were used. Intravenous iodinated contrast medium was used to determine mediastinal lymph node enlargement and/or the relation of lesions to adjacent vascular structures. The CT scans were evaluated by a study group including three chest physicians and a radiologist. A conclusion was reached by consensus. Pleural effusion was classified as unilateral and bilateral and massive and moderate. Massive pleural effusion was defined as the effusion occupying more than half of the hemithorax. Pleural thickening was classified as diffuse, nodular, and mass lesion. Diffuse pleural thickening was defined as a diffuse pleural thickness V 10 mm. Nodular pleural thickening was defined as focal pleural thickening between 10 and 30 mm. Pleura-based soft tissue mass with a width of z 30 mm or more was defined as mass lesion. Transversal or craniocaudal pleural thickening b 50 mm in length was defined as pleural plaque. Involvement of mediastinal pleura is defined as pleural thickening bordering the mediastinum. Involvement of interlobar fissures was defined as thickening of the pleural surfaces of the interlobar fissure. Mediastinal shift was defined as dislocation of the mediastinal structures due to pleural lesions. Volume contraction was defined as contraction of the involved hemithorax or mediastinal displacement, distortion of bronchovascular structures, elevation of ipsilateral hemidiaphragm, and compansatory hyperinflation of contralateral lung. Mediastinal lymph nodes were considered as pathologically enlarged when their short-axis diameter was longer than 10 mm in the transverse plane. Supplementary radiological findings such as involvement of pericardium, diaphragmatic pleura, chest wall, lung parenchyma, pneumothorax, and calcified pleural plaques were also noted. Statistical analysis was carried out using SPSS programme version 12.0 (SPSS Chicago IL, USA). Descriptive statistical tests were used for analysis of data. Mann-Whitney U test was used to compare differences in means of continuous variables. Any P value V .05 was considered to be statistically significant.
Forty-five male patients with a mean age of 56.8F 10.7 years (range: 30 –76), and 21 female patients with a mean age of 56.9F14.8 years (range: 35 –84) were included in the study. The mean age of all the patients was 56.8F 12.1 years (range: 30 –84). Male/female ratio was 2.1/1. There was not any significant difference between the mean ages of male and female patients ( P =.9). The overall mean age of 66 patients was 56.8F12.1 years (range: 30– 84). Nine patients (13.6%) were 40 years old or younger. The methods of diagnosis and histologic subtypes of the patients are presented in Table 1. The diagnosis of MPM was confirmed by histopathologic examination of pleural tissue samples obtained by closed pleural biopsy in 55 (83.4%), thoracoscopy in 6 (9.1%), thoracotomy in 2 (3%), and CT-guided percutaneous biopsy in 3 (4.5%) patients. The histologic subtypes were epithelial in 12 (18.2%), sarcomatous in 2 (3%), mixed in 4 (6%), and indifferentiated in 48 (72.8%) patients. The CT findings of the patients with MPM are listed in Table 2. Right hemithorax was affected more frequently (56.1%) than left hemithorax (42.4%). Bilateral involvement was found in only one (1.5%) patient. The most common CT finding was pleural effusion, which was present in 80.3% (n = 53) of the patients. The effusion was massive in 22 (41.5%) and moderate in 31 (58.5%) patients. The mediastinum was displaced to the contralateral side in eight patients (15%). Pleural thickening was present in 77.2% (n =51) of the patients. Pleural thickening was diffuse in
Table 2 CT findings of 66 patients with MPM Patients Radiological findings
n
%
Hemithorax involvement Right hemithorax Left hemithorax Bilateral hemithorax Pleural effusion Unilateral/bilateral Massive/moderate Pleural thickening Diffuse Nodular Mass lesion Calcified pleural plaques Involvement of mediastinal pleura Involvement of diaphragmatic pleura Involvement of interlobar fissures Involvement of lung parenchyma Volume contraction Mediastinal shift Lymphadenopathy Pericardial involvement Chest wall invasion Pneumothorax
37 28 1 53 52/1 22/31 51 9 31 11 8 21 4 19 4 25 8 6 4 6 2
56.1 42.4 1.5 80.3 98.1/1.9 41.5/58.5 77.2 17.6 60.8 21.6 12.1 31.8 6.1 28.8 6.1 37.9 12.1 9.1 6.1 9.1 3
F. O¨kten et al. / Clinical Imaging 30 (2006) 177–180
Fig. 1. Circumferential pleural thickening with mediastinal pleural involvement (A) and interlobar fissure involvement (B) in a patient with MPM.
17.6% (n = 9), nodular in 60.8% (n = 31), and mass type in 21.6% (n = 11) of these patients. The other CT findings were volume contraction in 25 (37.9%), mediastinal pleural involvement in 21 (31.8%), interlobar fissure involvement in 19 (28.8%), mediastinal shift in eight (12.1%), calcified pleural plaques in eight (12.1%), chest wall invasion in six (9.1%), lympadenopathy in six (9.1%), diaphragmatic pleural involvement in four (6.1%), lung parenchyma involvement in four (6.1%) patients, pericardial involvement in four (6.1%), and pneumothorax in two (3%) patients. Circumferential pleural thickening with mediastinal pleural involvement (Fig. 1A) and interlobar fissure involvement (Fig. 1B) are demonstrated in a patient with MPM in Fig. 1. 4. Discussion In the present study, we retrospectively reviewed the CT scans of 66 patients with MPM. The evaluation of CT scans demonstrated that pleural effusion, pleural thickening, volume contraction, involvement of mediastinal pleura, and interlobar fissure were the most common CT findings. Since the diagnosis of MPM was confirmed by histopathologic examination of pleural tissue samples obtained by
179
closed pleural biopsies in most of the cases (83.4%), the histologic subtypes were indifferentiated in 72.8% of the cases. Relatively small biopsies obtained by blinded closed pleural biopsy were not adequate for differentiating histologic subtypes. Therefore, we could not compare the CT findings of histologic subtypes. It is known that the latency period between initial exposure to asbestos and the development of MPM is long and averages 30 – 40 years [14] with a range as great as 14 – 72 years [15]. MPM due to previous occupational exposure to asbestos is usually diagnosed in the fifth to seventh decades of life, with a mean age of approximately 60 years [16]. Due to the early age at the onset of exposure, the mean ages of MPM patients with environmental asbestos exposure are lower. In the present study, the mean age was 56 years and a high ratio (13.6%) of the patients were 40 years old or younger. The youngest patient was 30 years old. A strong male predominance is present when occupational exposure to asbestos is involved. In the present study, there was not any occupational exposure to asbestos, but still, there was also a slight male predominance. This can be explained by the more frequent use of hospital services by the male population compared to females in rural parts of Turkey. CT is an accurate and reliable radiographic technique in diagnosing and determining the extent of mesothelioma. It can represent a significant improvement over chest radiography, although its sensitivity and specificity for predicting the malignant nature of diffuse pleural lesions based upon morphologic criteria are only 72% and 83%, respectively [12]. Furthermore, CT lacks sensitivity for detecting miliary pleural seeding and critical invasion into the mediastinum or through the diaphragm [17]. Although it is not pathognomonic, the most characteristic feature of MPM is the presence of extensive, lobular, thickened irregular pleural masses that involved all pleural surfaces including the mediastinum [18]. In the present study, CT findings revealed a slight rightsided predominance (56.1%) of involvement by MPM, which is compatible with the literature [19]. Pleural effusion was the most common finding and was present in 80.3% of the cases. Although it is not a specific finding for MPM, it is reported to be present in 72–100% of the cases in the literature [10,13,17,20]. In this study, pleural effusion was the only finding without any pleural lesion in four cases (6.1%). In the study of Xenyig˘it et al. [13], 3% of cases presented with pleural effusion without pleural thickening or pleural plaques. Yilmaz et al [4] detected isolated pleural effusion in 2.2% of the patients with MPM. Based on these findings, a possible diagnosis of MPM must not be excluded in the absence of pleural thickening. Although it is rare, MPM must be considered in the differential diagnosis of pleural effusion and a history of exposure to asbestos. Pleural thickening was the second most common CT finding, which was present in 77.2% of the patients. It was mostly nodular (60.8%) in nature. Diffuse pleural thickening
180
F. O¨kten et al. / Clinical Imaging 30 (2006) 177–180
can be a manifestation of benign asbestos exposure, but when nodular thickening was present, it is difficult to distinguish it from MPM [21]. Leung et al [12] also reported that nodular pleural thickening was present in 63% of their MPM cases. Pleural plaques are the most common radiological manifestations of asbestos exposure. The presence of calcification suggests a benign process [12,18,22]. Although calcified plaques may be seen in MPM cases, they are uncommon [18]. In this study, calcified pleural plaques were present in eight patients (12.1%). Therefore, MPM must be considered in the differential diagnosis of calcified pleural plaques, especially when there is accompanying pleural effusion [3]. Irregular or nodular interlobar fissure involvement can be an early finding of MPM detected by CT. Free or localized pleural effusion and pleural thickening resulting from fibrosis can also involve the interlobar fissures. These were reported to cause smooth thickening of the fissures rather than the irregular or nodular thickening produced by MPM [10]. Interlobar fissure involvement was reported to be present in 53– 86% of the cases [3,13,14,22]. In the present study, it was present in 28.8% of the cases. Volume contraction resulting from the involvement of pleura is a common finding of MPM. The fixation of the mediastinum and volume contraction at the involved site are suggested as diagnostic features of MPM, but they may also be present in some benign and malign diseases of the chest [22]. Several studies had reported volume contraction in 42–73% [5,12–14,22]. In the present study, it was present in 37.9% of the cases. Involvement of lung parenchyma can be as pleural-based nodular masses extending into the lung or round, sharply demarcated masses located within the lung [18]. In this study, we detected parenchymal involvement in four patients (6.1%), and all were pleural-based masses extending into the lung. Xenyig˘it et al [13] reported lung penetration in 10% of their patients. On CT scans, enlarged lymph nodes may be seen in up to 50% of patients [17]. In this study, they were present in 9.1% of the cases. The results of this study, together with several other studies, range in a wide interval. This can be a result of different study populations at different stages of their diseases. In conclusion, pleural effusion, pleural thickening, volume contraction, involvement of mediastinal pleura, and interlobar fissure were the most common CT findings of MPM. Although none of these findings are pathognomonic for MPM, they may provide valuable clues for the differential diagnosis, at least in patients with a history of asbestos exposure. References [1] Albelda SM, Sterman DH, Litzky LA. Malignant mesothelioma and other primary pleural tumors. In: Fishman AP, editor. Fishman’s pulmonary diseases and disorders. New York7 McGraw-Hill, 1988. pp. 1453 – 66.
[2] Hillerdal G. Mesothelioma: cases associated with nonoccupational and low dose exposures. Occup Environ Med 1999;56:505 – 13. [3] Selc¸uk ZT, C ¸ fplq L, Emri S, Kalyoncu AF, Xahin AA, BarVY YI. Malignant pleural mesothelioma due to environmental mineral fiber exposure in Turkey: analysis of 135 cases. Chest 1992;102:790 – 6. [4] YVlmaz UM, Utkaner G, YalnVz E, Kumcuog˘lu Z. Computed tomographic findings of environmental asbestos-related malignant pleural mesothelioma. Respirology 1998;3:33 – 8. [5] Xahin AA, C ¸ fplq L, Selc¸uk ZT, EryVlmaz M, Emri S, Akhan O, BarVY YI. Malignant pleural mesothelioma caused by environmental exposure to asbestos and erionite in rural Turkey: CT findings in 84 patients. AJR Am J Roentgenol 1993;161:533 – 7. ¨ zesmi M, Kerse I, O ¨ zer E, Kolacan B, [6] BarVY YI, Xahin AA, O Altinors M, Goktepeli A. An outbreak of pleural mesothelioma and ¨ rgqp in Anatolia. chronic fibrosing pleurisy in the village of Karain/U Thorax 1978;33:181 – 92. [7] Artvinli M, BarVY YI. Environmental fiber-induced pleuro-pulmonary diseases in an Anatolian village: an epidemiological study. Arch Environ Health 1982;37:177 – 81. [8] BarVY I, Simonato L, Artvinli M, Pooley F, Saracci R, Skidmore J, Wagner C. Epidemiological and environmental evidence of the health effects of exposure to erionite fibers: a four year study in the Cappadocian region of Turkey. Int J Cancer 1987;39:10 – 7. [9] MetintaY M, Hillerdal G, MetintaY S. Malignant mesothelioma due to environmental exposure to erionite: follow-up of a Turkish emigrant cohort. Eur Respir J 1999;13:523 – 6. [10] Adams VI, Unni KK, Muhm JR, Jett JR, Ilstrup DM, Bernatz PE. Diffuse malignant mesothelioma of pleura. Diagnosis and survival in 92 cases. Cancer 1986;58:1540 – 51. [11] Henderson DW, Shilkin KB, Whitaker D. Reactive mesothelial hyperplasia vs mesothelioma, including mesothelioma in situ: a brief review. Am J Clin Pathol 1998;110:397 – 404. [12] Leung AN, Mqller NL, Miller RR. CT in differential diagnosis of diffuse pleural disease. AJR Am J Roentgenol 1990;154:487 – 92. [13] Xenyig˘it A, Bayram H, Babayig˘it C, Topc¸u F, Nazarog˘lu H, Bilici A, Leblebici I˙H. Malignant pleural mesothelioma caused by environmental exposure to asbestos in the southeast of Turkey: CT findings in 117 patients. Respiration 2000;67:615 – 22. [14] Erzen C, EryVlmaz M, Kalyoncu F, Bilir N, Xahin A, BarVY YI. CT findings in malignant pleural mesothelioma related to nonoccupational exposure to asbestos and fibrous zeolite (erionite). J Comput Assist Tomogr 1991;15:256 – 60. [15] Bianchi C, Giarelli L, Grandi G, Brollo A, Ramani L, Zuch C. Latency periods in asbestos-related mesothelioma of the pleura. Eur J Cancer Prev 1997;6:162 – 6. [16] Boutin C, Schlesser M, Frenay C, Astoul Ph. Malignant pleural mesothelioma. Eur Respir J 1998;12:972 – 81. [17] Rusch VW, Godwin JD, Shuman WP. The role of computed tomography scanning in the initial assessment and follow-up of the malignant pleural mesothelioma. J Thorac Cardiovasc Surg 1988;96: 171 – 7. [18] Rabinowitz JG, Efremidis SC, Cohen B, Dan S, Efremidis A, Chahinian AP, Teirstein AS. A comparative study of mesothelioma and asbestosis using computed tomography and conventional chest radiography. Radiology 1982;144:453 – 60. [19] Pistolesi M, Rusthoven J. Malignant pleural mesothelioma. Update, current management, and newer therapeutic strategies. Chest 2004; 126:1318 – 29. [20] YazVcVog˘lu S, ˙Ilc¸ayto R, BalcV K, SaylV BS, Yorulmaz B. Pleural calcification, pleural mesotheliomas, and bronchial cancers caused by tremolite dust. Thorax 1980;35:564 – 9. [21] Miller WT, Gefter WB, Miller WT. Asbestos-related chest diseases: plain radiographic findings. Semin Roentgenol 1992;27: 102 – 20. [22] Kawashima A, Libshitz HI. Malignant pleural mesothelioma: CT manifestations in 50 cases. AJR Am J Roentgenol 1990;155: 965 – 9.