A case of anisakiasis that presented as a submucosal tumor at the ascending colon

A 57-year-old female underwent colonoscopy for follow-up after resection of a rectal carcinoid tumor. A submucosal tumor of 1.5 cm in diameter was detected at the ascending colon. The tumor had a few small depressions on the mucosa. Endoscopic ultrasound revealed a low echoic tumor including high echoic parts. She underwent laparoscopic-assisted ascending colectomy. Microscopically, the tumor consisted of necrotic tissue including an Anisakis body and granulomatous tissue. After the histological diagnosis was made, her serum was found to be positive for the antibody to Anisakis. This tumor was found incidentally and caused no symptoms. Anisakiasis is usually an infection of the stomach and most patients have severe acute abdominal symptoms. We experienced silent anisakiasis of the ascending colon.