Isolated metastases to the common iliac and mesorectal lymph nodes suggesting an atypical metastatic route in upper rectal cancer: A case report

INTRODUCTION: Most lymphatic vessels in the upper rectum run parallel to the superior rectal artery and up to the inferior mesenteric artery. Here, we report a rare case of upper rectal cancer with atypical lymphatic spread. PRESENTATION OF CASE: A 39-year-old woman was diagnosed with upper rectal cancer and isolated lymph node (LN) metastases to the mesorectal and right common iliac LNs. The patient underwent laparoscopic low anterior resection with targeted dissection of the right common iliac LNs. The pathological diagnosis was T3N2M0, and the patient received postoperative adjuvant chemotherapy. One year later, local recurrence was found at the sacral promontory level, where the targeted lymphadenectomy had been performed previously. The recurrent tumor was surgically resected together with the attached presacral fascia. The patient subsequently received postoperative adjuvant chemotherapy, and there was no recurrence one year after the last surgery. DISCUSSION: Isolated metastases were observed in the right common iliac and mesorectal LNs. The locally recurrent tumor included lymphatic vessels running along the median sacral artery. No metastatic tumor was found in the internal iliac area at the time of the initial diagnosis nor during recurrence. Thus, this case suggests the presence of a rare metastatic route from the mesorectal LN to the common iliac LN via the median sacral lymphatics. CONCLUSION: Lymphatic spread of rectal cancer may be predictable; however, rare patterns of LN metastasis can exist. The assessment of lymphatic flow is crucial for improving the oncological outcomes of rectal cancer surgery.