Malignant Pleural Mesothelioma Caused by Environmental Exposure to Asbestos in the Southeast of Turkey : CT Findings in 117 Patients

Background and Objectives: Malignant pleural mesothelioma (MPM) is reported to be common in the southeast of Turkey, as a result of environmental asbestos exposure. The aim of this study was to evaluate the computed tomography (CT) features of MPM in patients with a history of asbestos exposure. Methods: The CT scans of 117 patients who had a diagnosis of MPM were retrospectively evaluated. Additionally, CT findings of histologic subtypes were compared. Results: The most common CT findings included pleural effusion (n = 104, 89%), pleural thickening (n = 96, 82%), mediastinal pleural involvement (n = 77, 66%) and interlobar fissural involvement (n = 62, 53%). Histologic subtype analysis was performed in 89 patients; of these, epithelial, sarcomatous and mixed types were identified in 46, 23 and 20 patients, respectively. An analysis of CT findings demonstrated that the involvement of mediastinal pleural (91%), interlobar fissure (87%) and lung parenchyma (48%) was significantly more frequent in sarcomatous type, as compared to epithelial (61% and p ! 0.01; 35 and 4%, p ! 0.0001, respectively) and mixed types (65% and p ! 0.05; 10% and p ! 0.0001; 10% and p ! 0.01, respectively). Furthermore, there was a significant correlation between pericardial involvement and chest wall involvement (r = 0.42, p ! 0.05) in sarcomatous type. Similarly, lymphadenopathy and parenchymal involvement (r = 0.23, p ! 0.02), pericardial and chest wall involvement (r = 0.25, p ! 0.01), chest wall and interlobar fissural involvement (r = 0.25, p ! 0.01) were significantly correlated, when CT findings of all histologic subtypes were combined. Conclusions: These results suggest that although CT findings of MPM vary, they may provide valuable clues to the diagnosis, at least in patients with a history of asbestos exposure. In addition, the presence of extensive lesions may suggest MPM of sarcomatous subtype. Copyright © 2000 S. Karger AG, Basel D ow nl oa de d by : D ic le Ü ni ve rs ite si 21 2. 17 5. 24 4. 14 6 1/ 8/ 20 14 1 0: 17 :1 5 A M 616 Respiration 2000;67:615–622 Şenyı̇ğı̇t/Bayram/Babayı̇ğı̇t/Topçu/ Nazaroğlu/Bı̇lı̇cı̇/Leblebı̇cı̇ Introduction Malignant pleural mesothelioma (MPM) is a primary pleural tumor of mesodermal origin [1]. In the etiology, exposure to asbestos fibers is the most frequent cause, though fibrous zeolite (erionite) and radiation are also among the etiologically important factors [2–6]. MPM is endemically present in some regions of Turkey including several provinces in the southeast of the country, as a result of exposure to environmental fibrous minerals [7]. Yazıcıoğlu [8] and Yazıcıoğlu et al. [9] previously reported that people born or living in some districts of Diyarbakır, Elazıg and Şanlıurfa are exposed to soil containing serpentine and amphibole asbestos fibers and talc, which have no economic value. The material containing asbestos is quarried from mountains by men for both local use and sale in neighboring towns. It is used as a whitewash material for the walls and floors of the houses, and this procedure is repeated every year. Thus, householders are repeatedly exposed to asbestos fibers in their environment, from an early age [9, 10]. The diagnosis of pleural mesothelioma is difficult and often delayed for 6–8 months after the initial symptoms [11]. Cytological examination of pleural effusion, percutaneous transthoracic needle biopsy and even diagnostic thoracoscopy are sometimes insufficient for diagnosis [12]. In such circumstances computed tomography (CT), as a noninvasive procedure, may contribute to the diagnosis, although none of the findings are pathognomonic [13]. In this study, we have evaluated CT findings in 117 cases of MPM caused by environmental exposure to asbestos fibers. We have also investigated the frequency of CT findings in patients whose histologic subtype of disease was identified. Materials and Methods The CT scans of 117 patients (67 men and 50 women) who were diagnosed as having MPM at the Departments of Chest Diseases and Tuberculosis, and Chest Surgery, Dicle University Research Hospital, Diyarbakır, Turkey, between January 1988 and March 1999 were retrospectively evaluated. All patients had a history of environmental asbestos exposure, and their mean age was 53.2 years with a range of 21–79 years. The diagnosis was made on the basis of pleural tissue obtained using Ramel needle biopsy, cytologic examination and by videoassisted thoracoscopic surgery (VATS) in 96 (82%), 8 (7%), and 13 cases (11%), respectively. Thirteen patients had no pleural effusion; of these, 4 were diagnosed by VATS, 3 by transthoracic needle biopsy, and 6 by CT or ultrasonography-guided Ramel needle biopsy. The diagnoses of MPM were pathologically confirmed in all cases, and the histologic subtype, where noted, was included. Thorax CT was performed in all cases after hospitalization, using a Toshiba TCT 600S CT device and Toshiba X vision GX (Otowara City, Naso, Japan). Evaluation was carried out in chest images obtained in 10-mm slices from the apices of the lungs to costophrenic angles. All of the sections were taken in the supine position at the end of the inspirium. Both mediastinal and parenchymal window settings were used. Intravenous iodinated contrast medium was given to the patients with normal respiratory function to determine mediastinal lymph node enlargement and/or the relation of the lesions to adjacent vascular structures. The CT scans were evaluated by a team of 3 pneumologists and 4 radiologists. A conclusion was reached by consensus. On CT scans, pleural thickening was classified as diffuse, mass type and nodular, and the localization of pleural effusion as ipsilateral and bilateral. In cases of different types of pleural thickening in the same individual, each type was noted separately. Dislocation of the mediastinal structures due to pleural lesions was defined as ‘mediastinal shift’. Contraction of the involved hemithorax or mediastinal displacement, distortion of the bronchovascular structures, elevation of the ipsilateral hemidiaphragm and compensatory hyperinflation of contralateral lung were evaluated as ‘volume contraction’. Thickening of the pleura of 10 mm or less was defined as ‘pleural thickening’, and 10–30 mm focal pleural thickening as ‘pleural nodule’. Pleura-based soft tissue mass with a width of 30 mm or more was referred to as ‘pleural mass’. Transversal or craniocaudal pleural thickening less than 50 mm in length was noted as ‘pleural plaque’. Mediastinal lymph nodes were considered pathologically as enlarged, if they were greater than 10 mm in short-axis diameter in the transverse plane. Involvement of interlobar fissures and mediastinal pleura were also noted. Furthermore, an association between CT findings and histologic subtypes (i.e. epithelial, sarcomatous and mixed) was investigated in cases whose histologic subtype of disease was identified. Statistical Analysis Student’s t test was applied to determine the significance of any differences between CT findings in subgroups of patients with epithelial, sarcomatous or mixed histologic subtypes. Furthermore, the association between CT findings within histologic subtypes was tested using Pearson’s correlation coefficient, and all values of p ! 0.05 were considered to be significant.