A case of urinary ascites due to desmoid tumor during follow-up of familial adenomatous polyposis

Abstract

　Familial adenomatous polyposis （FAP） is caused by germline mutation of the APC gene. Desmoid tumors are found in 8-20% of patients with FAP. Present case was a 28 years old woman without a history of abdominal surgery. After diagnosis of FAP at 16 years old, she underwent periodic endoscopic polypectomy for colonic polyps and endoscopic submucosal dissection for mucosal gastric cancer. She visited our hospital with abdominal fullness. CT and MRI showed a large amount of ascites and 40mm-size cystic tumor near the left ureter and left hydronephrosis. We suspected gynecologic malignancy, desmoid tumor, or peritoneal cancer. Exploratory laparoscopy revealed massive urinary ascites with the retroperitoneal tumor involving the left ureter. We performed combined resection of the tumor and left ureter followed by ureteroureteral anastomosis. The tumor was pathologically diagnosed as a desmoid tumor. Desmoid tumor is known as one of the extraintestinal manifestations of FAP, but the case with urinary ascites is extremely rare.