Cytological Assessment of Desmoplastic Malignant Pleural Mesothelioma in an Autopsy Case

Introduction Desmoplastic malignant pleural mesothelioma (DMPM) is a sarcoma type mesothelioma, comprising about 5% of malignant pleural mesotheliomas. Although effusion cytology is commonly used as the primary diagnostic approach for mesothelioma, this may not be useful for DMPM due to its desmoplastic nature and bland cellular atypia. We hereby report a case of DMPM diagnosed through autopsy along with its cytological features that have not been described previously. Case presentation A male in his 60s with a history of occupational asbestos exposure was referred to our hospital with right chest pain. Chest computed tomography scan showed right pleural effusion. Thirteen months later, the patient died of respiratory failure. In autopsy, the scrape-imprint smear and the pleural effusions cytology were performed. The scrape-imprint smear samples exhibited spindle cells with mild nuclear atypia and grooves with fibrous stroma. In the pleural effusion cytology, spindle cells having mild nuclear atypia and grooves with loose epithelial connections were observed. Histological examination of the right pleura showed spindle cells proliferating with dense collagen fibers, as seen in cytological samples, thus rendering the diagnosis of DMPM. Diagnosis was confirmed by fluorescence in situ hybridization. Conclusion Cytological procedures, such as pleural effusion cytology and scrape-imprinting method, may be useful as an ancillary tool in the diagnosis of rare tumors such as DMPM.