A desmoid tumor with fluorodeoxyglucose accumulation arising from the anastomotic site of postoperative gastric cancer: a case report

BACKGROUND: Desmoid tumors are extremely rare borderline benign and malignant tumors that do not exhibit accumulation on fluorodeoxyglucose positron emission tomography–computed tomography. In the present study, we report a rare case of a desmoid tumor with fluorodeoxyglucose accumulation at the anastomotic postoperative gastric cancer site. CASE PRESENTATION: A 68-year-old Japanese man underwent robot-assisted laparoscopic distal gastrectomy for early-stage gastric cancer in 2019. The pathological diagnosis was stage IA cancer, and no adjuvant chemotherapy was administered. Two years after surgery, a soft mass appeared on the greater curvature side of the anastomosis on computed tomography. Fluorodeoxyglucose positron emission tomography–computed tomography revealed fluorodeoxyglucose accumulation, which suggested a malignancy; therefore, surgery was performed for diagnostic treatment. The histopathological findings led to the diagnosis of a desmoid tumor. The patient has not experienced recurrence to date. CONCLUSIONS: In the present study, we encountered a desmoid tumor arising from the anastomotic site of a postoperative gastric cancer. This case is rare as fluorodeoxyglucose positron emission tomography–computed tomography showed fluorodeoxyglucose accumulation in the desmoid tumor, and a preoperative diagnosis could not be reached. We hope that further studies will improve the accuracy of preoperative diagnosis.