OBJECTIVE: Malignant pleural mesothelioma in rural Turkey frequently results 
from environmental exposure to tremolite asbestos or fibrous zeolite (erionite). 
The aim of this study was to determine the CT features of malignant pleural 
mesothelioma in patients exposed to asbestos or erionite.
MATERIALS AND METHODS: The CT scans of 84 patients with proved malignant pleural 
mesothelioma were retrospectively evaluated. Twenty patients (24%) had been 
exposed to erionite and 64 patients (76%) had been exposed to asbestos. The CT 
scans were interpreted by seven observers who did not know the clinical or 
pathologic findings.
RESULTS: CT scans showed either unilateral pleural thickening or pleural 
nodules/masses in all patients. Pleural nodules were present in 25 patients 
(30%) and pleural masses in 44 patients (52%). Pleural effusion was found in 61 
patients (73%), mediastinal pleural involvement in 78 (93%), pleural 
calcifications in 52 (62%), involvement of the interlobar fissures in 64 (76%), 
and volume contraction in 61 (73%). Reduced size of the hemithorax was 
significantly correlated with chest wall involvement. On the basis of CT 
findings, the preassigned staging was changed in 21 patients (25%), including 
44% of the patients with disease that had been classified as stage I. CT 
findings were not significantly different between the patients exposed to 
erionite and those exposed to asbestos.
CONCLUSION: The most common CT findings in cases of malignant pleural 
mesothelioma were unilateral pleural thickening or pleural nodules/masses with 
or without effusion. CT provided valuable information on the extent of the 
disease, which was important for staging. Although the CT features are not 
pathognomonic, they provide valuable clues to the diagnosis in patients who have 
been exposed to mineral fibers.