Metastatic pleural mesothelioma presenting initially as multiple gastric and colonic polyps

It is extremely rare for malignant mesothelioma to present as gastrointestinal polyps. This case report documents the presentation of malignant mesothelioma in a 72-year-old as rectal bleeding and weight loss. Endoscopically, there were multiple gastric and colonic polyps. Histopathologically, there were atypical cells in the lamina propria with benign surface epithelium. The cells tested positive for cytokeratin, calretinin and D2-40 and negative for CD45, CD117, Ber-EP4 and CEA, confirming the diagnosis of metastatic mesothelioma. A computed tomography scan of the chest showed nodular thickening of the left lower pleura that was compatible with a diagnosis of primary pleural mesothelioma. We conclude that metastatic mesothelioma can sometimes present as gastrointestinal polyps.