pleural thickening pleural thickening pleural thickening is an increase in the bulkiness of one or both of the pulmonary pleurae. pleural thickeningmacroscopic appearance of a pleural plaque.specialtyrespirology causes categorydiseasefeatures infection after empyema most often basolateral may have calcification non-progressive after tuberculosis commonly forming an apical pleural cap non-progressive rarely extensive, with sheet-like calcifications active infection with mycobacteria other than tuberculosis, or chronic pulmonary aspergillosis slowly progressive apical distribution cavitations non-infectious inflammation asbestosis pleural plaques (see section below) less common: extensive confluent thickening, sometimes with pleural effusion after pleurodesis diffuse non-progressive after hemothorax usually basolateral distribution may have calcification non-progressive after drugs, such as methysergide or bromocriptine diffuse possible interstitial pulmonary fibrosis cancer-related primary cancer, mainly mesothelioma associated with asbestosis progressive thickening metastasis or invasion, mainly from lung cancer progressive nodular changes lung tumors pleural plaques pleural plaques are patchy collections of hyalinized collagen in the parietal pleura. they have a holly leaf appearance on x-ray. they are indicators of asbestos exposure, and the most common asbestos-induced lesion. they usually appear after 20 years or more of exposure and never degenerate into mesothelioma. they appear as fibrous plaques on the parietal pleura, usually on both sides, and at the posterior and inferior part of the chest wall as well as the diaphragm.