Malignant Peritoneal Mesothelioma Masquerades as Peritoneal Metastasis on ¹⁸F-FDG PET/CT Scans; a Rare Diagnosis that Should Not Be Missed

Malignant peritoneal mesothelioma (MPM) is a rare but fatal tumor. The clinical presentations and imaging findings are nonspecific and resemble various diseases, including peritoneal metastasis. Imaging findings of MPH on ¹⁸F-¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT) are diverse and not well described. We report the two cases of biopsy-proven MPH using ¹⁸F-FDG PET/CT. In our cases, interesting disease patterns—including MPH arising from visceral peritoneal lining of kidney that suffer from polycystic disease and from the parietal peritoneum beneath the appendectomy scar—were presented. One case showed classical metastases localized within the abdominal cavity; while the other case exhibited the rare pattern of extensive multi-organ metastases. By knowing the possible variations and diagnostic pitfalls of ¹⁸F-FDG PET/CT findings in MPM, more accurate interpretation of such mysterious cancer is attainable.