Cytological Assessment of Desmoplastic Malignant Pleural Mesothelioma in an Autopsy Case

Introduction: Desmoplastic malignant pleural mesothelioma (DMPM) is a sarcoma-type mesothelioma, comprising approximately 5% of malignant pleural mesotheliomas. Although effusion cytology is com-monly used as the primary diagnostic approach for mesothelioma, it may not be useful for DMPM be-cause of the presence of desmoplasia and bland cellular atypia. We report a case, and previously unde-scribed cytological features, of DMPM that was diagnosed during autopsy.Case Presentation: A man in his 60s with a history of occupational asbestos exposure was referred to our hospital with right chest pain. A chest CT scan showed right pleural effusion. Thirteen months later, the patient died of respiratory failure. During autopsy, scrape-imprint smears were prepared and cytol-ogy of pleural effusions was performed. The scrape-imprint smear samples showed spindle cells with mild nuclear atypia and grooves with fibrous stroma. Pleural effusion cytology revealed spindle cells with mild nuclear atypia, as well as grooves with loose epithelial connections. Histological examination of the right pleura showed spindle cells proliferating with dense collagen fibers, as seen in the cytologi-cal samples, thus indicating a diagnosis of DMPM, which was confirmed by fluorescence in situ hy-bridization.Conclusion: Cytological procedures such as pleural effusion cytology and scrape-imprinting cytology may help in diagnosing rare tumors such as DMPM. (J Nippon Med Sch 2022; 89: 616?622)