Intra-abdominal Fibromatosis Arisen Near the Gastric Remnant Mimicking Recurrence of Gastrointestinal Stromal Tumor of the Stomach—A Case Report—

Abstract

The patient was a 50-year-old man who underwent laparoscopic distal gastrectomy for gastrointestinal stromal tumor (GIST) of the stomach with lymph node metastasis at the age of 48. He was classified as a patient at high risk of developing recurrence by the Fletcher's classification and imatinib mesylate was administered after the surgery. A CT scan revealed a 2-cm solid mass in the perigastric mesentery 18 months after the GIST surgery. Recurrence of GIST was clinically suspected and he underwent the resection of the tumor with a part of the gastric wall to where the tumor continued. The resected tumor was elastic-hard and the section was white and solid. Histopathology revealed the growth of spindle-shaped tumor cells surrounding collagen fiber progression ; no mitosis was found. Since c-kit, CD34, and DOG-1 were negative and nuclear β-catenin was positive on immunohistochemical staining, he was diagnosed with intra-abdominal fibromatosis (IAF). It may be impossible to distinguish between GIST and IAF clinically. So far no cases of gastric GIST associated with IAF have been reported in Japan. We here report a rare case of IAF that developed during imatinib administration and mimicked recurrence of GIST of the stomach.