Anisakidosis of the sigmoid colon disguising as metastatic carcinoma: a case report and review of the literature.

Intestinal anisakidosis is a rare nematode infestation caused by the ingestion of larvae-infected raw or undercooked fish. Most cases are incidentally diagnosed during surgery for other reasons. We present such a case of anisakid larvae seen in a patient's sigmoid colon resected for adenocarcinoma, where a subserosal nodule caused by the inflammatory reaction to the worm was presumed to be a lymph node involved by metastatic tumor. With the increasing popularity of raw fish consumption, the incidence of this parasitic infection is bound to increase, requiring surgical pathologists to be cognizant of its existence and aware of its histologic appearance.