[A Case of Postoperative Recurrence of Sigmoid Colon Cancer That Was Diagnosed as a Result of Cervical and Mediastinal Lymph Node Metastasis].

An 81-year-old woman was referred to our hospital with sigmoid colon cancer 2 years ago. The patient underwent laparoscopic sigmoidectomy. According to the ninth edition of the TNM classification, the pathological diagnosis was pStage Ⅲa (pT1bN1bM0). However, adjuvant chemotherapy was not administered, in compliance with the patient's wishes. Thoracoabdominal computed tomography(CT)performed 2 years after the surgery revealed numerous enlarged lymph nodes in the neck and mediastinum and around the upper abdominal aorta, with no evidence of liver metastasis, lung metastasis, or peritoneal dissemination. The serum carcinoembryonic antigen level was elevated at 5.1 ng/mL. A CT scan obtained 6 months ago showed no obvious signs of recurrence, and the disease progressed rapidly, with only enlarged lymph nodes. Therefore, we considered possibilities other than colorectal cancer recurrence, such as malignant lymphoma or small-cell lung cancer. Cervical lymph node biopsy detected adenocarcinoma, and the immunohistochemical examination results were consistent with lymph node recurrence of colorectal cancer. Although the patient received systemic chemotherapy, she died approximately 9 months after recurrence. Herein, we report a case of postoperative recurrence of sigmoid colon cancer diagnosed as a result of cervical and mediastinal lymph node metastasis, which is a relatively rare form of colorectal cancer recurrence.