Two Cases of Advanced/Recurrent Rectal Cancer which showed False-Positive for Para-Aortic Lymph Node in FDG-PET/CT

Abstract

¹⁸F-fluorodeoxy-glucose positron emission tomography (FDG-PET) has been used in malignancy diagnosis, but its utility remains unclear. We report 2 case studies of advanced and recurrent rectal cancer in which FDGPET/CT detected paraaortic lymph nodes (No.216 lymph node) to be false by positive. Case 1: A 69-year-old woman with advanced low rectal cancer was found in computed tomography (CT) to have lymph node swelling around the primary tumor and abdominal aorta. Abnormal concentrations were confirmed by FDG-PET/CT, necessitating low anterior resection with hysterectomy and D3+No.216 dissection. Histopathological results indicated that all removed lymph nodes were negative for metastasis. Case 2: A 54-year-old woman with local and lymph node recurrence after abdominoperineal resection of the rectum was found in FDGPET/CT to have abnormal concentrations in the local recurrent tumor and No.216 lymph node, necessitating resection of the recurrent tumor, resection of the posterior wall of the vagina together with the coccygeal bone, and removal of the No.216 lymph node. Histopathological results showed no metastasis in any lymph node. Because FDG-PET/CT may show false positivity for lymph nodes in some cause of advanced or recurrent rectal cancer, it is important not to miss an opportunity for curative resection by conducting intraoperative frozen section examination.