[Malignant peritoneal mesothelioma detected by endoscopy after intractable stuttering:a case report]

A male patient in his 70s visited our hospital with persistent vomiting and hiccups. The barium enema demonstrated poor extension from the hepatic flexure to the middle of the transverse colon, with a fold companion on the side of the mesenteric attachment and lateral deformity. A colonoscopy revealed ulceration and submucosal tumor-like elevation, and the lumen was laterally deformed, indicating metastatic malignancy with peritoneal tumor dissemination. A computed tomography scan revealed fatty tissue opacity in the mesentery of the transverse colon and mild lymphadenopathy with heterogeneous contrast effect. Biopsy was suspicious of neuroendocrine carcinoma, and laparoscopically-assisted extended right semicolon resection was performed. Macroscopically, the tumor protruded on the serosal surface and invaded the colonic wall, probably causing digestive symptoms. Microscopically, the tumor was composed of sheets or nests or cribriform structures of atypical epithelioid cells, together with areas of the spindle or stellate-shaped cells with myxoid stroma. Immunohistochemically, the tumor cells were positive for cytokeratin, calretinin, WT-1, and D2-40 and negative for CEA, p63, and claudin-4. The histopathological diagnosis included biphasic malignant mesothelioma.