A Case of Extra Gastrointestinal Anisakiasis Mimicking Dissemination Metastasis after Operation for Advanced Rectal Cancer

Abstract

A 59-year-old man underwent abdominoperineal resection and lateral pelvic lymph node dissection with resection of the left external iliac vein after chemoradiography for rectal cancer with bulky lymph node metastasis. The pathological diagnosis was ypStage IIIb, and adjuvant chemotherapy was conducted. Two years after the surgery, an abdominal computed tomography revealed a nodule just below the abdominal wall. Slight accumulation of FDG (standardized uptake value, 1.7) to the nodule was demonstrated on the combined positron emission tomography and computed tomography (PET-CT). The nodule was suspected to be dissemination metastasis. As no other metastases were confirmed, laparoscopic resection for the nodule was performed. During surgery, a white nodule was identified in the greater omentum which was histopathologically found to be a foreign body granuloma due to an anisakis larva. He was diagnosed with extra gastrointestinal anisakiasis.

Preoperative diagnosis of this disease is very difficult because it is rare and may be asymptomatic. We must be attentive to this rare disease as a differential diagnosis of an intra-abdominal nodule after operation for advanced rectal cancer.