A Case of an Eosinophilic Granuloma Mimicking a Submucosal Tumor in the Ascending Colon Probably Caused by Anisakis

Anisakiasis in the gastrointestinal tract is caused by the ingestion of raw marine fish that contain Anisakis lavae. In rare cases, Anisakiasis is found as an eosinophilic granuloma that mimics a submucosal tumor. The diagnosis is usually made after surgical resection. Several cases of gastric anisakiasis imitating a submucosal lesion have been reported. However, colonic anisakiasis forming a submucosal lesion is very rare and only a few cases have been reported. All of the cases were confirmed after surgery. Recently, we encountered a male patient with a submucosal lesion on the ascending colon during a health screening. Several biopsies were performed on the same site as the lesion. The pathological finding was eosinophilic granuloma. We tentatively diagnosed the patient with eosinophilic granuloma due to Anisakis as the patient consumed raw seafood and eosinophilia was detected on a laboratory test. We decided not to perform any procedure. One month later, the eosinophilic granuloma disappeared as seen on a follow-up colonoscopy. (Korean J Gastrointest Endosc 2008;37:127-131)