Metastatic spread of pleural mesothelioma to the peritoneum and gallbladder presenting as recurrent acute cholecystitis.

Malignant pleural mesothelioma, a rare, aggressive cancer primarily associated with asbestos exposure, is characterised by poor prognosis and limited treatment options. Distant metastases are uncommon, and peritoneal involvement is rare, while metastasis to the gallbladder is extremely unusual. We report the case of a patient with malignant pleural mesothelioma undergoing immunotherapy with nivolumab and ipilimumab, who developed recurrent acute cholecystitis. Imaging revealed features of acute cholecystitis with gallstones. She eventually underwent a laparoscopic cholecystectomy because immunotherapy could not be continued in the presence of infection. Histopathological and immunohistochemical analysis confirmed metastatic epithelioid mesothelioma. The gallbladder metastasis was likely haematogenous or from peritoneal seeding, rather than direct spread. This case underscores the importance of a high index of suspicion when evaluating atypical presentations of mesothelioma, particularly in the context of immunotherapy.