Abstract
We report a rare case of malignant peritoneal mesothelioma growing in the lower mesorectum. A 46-year-old woman was suspected to have an ovarian tumor by ultrasound examination performed at a regular medical check. Both barium enema and colonoscopy showed the compression extraluminally from the wall of the lower rectum. Abdominal CT scan showed a tumor of approximately 8 cm around the lower rectum, which partly contained internal necrosis. Pelvic MRI showed the tumor contained cystic and solid lesion. FDG-PET showed increased tumor uptake of FDG. A low anterior rectal resection was performed to excise the tumor. Intraoperative findings showed an 80×50×81 mm sized tumor growing in the lower mesorectum without peritoneal metastasis. The histopathological and immunohistochemical examination of resected specimen showed the tumor to be showed malignant peritoneal mesothelioma, with cells staining positively for calretinin, cytokeratin 5/6 and D2-40, negatively for CEA and MOC-31. The patient has had no recurrence one year after surgery without adjuvant therapy. Malignant peritoneal mesothelioma mostly grows in the intraperitoneal lesion. This report is a second case in Japan, which reported malignant peritoneal mesothelioma growing at lower mesorectum.
