Lymph node metastasis in a patient with carcinoma in situ rectal cancer: A case report

Colorectal cancer typically progresses from intramucosal carcinoma to invasive cancer, with lymph node metastasis considered possible only after submucosal invasion. Tumors confined to the mucosa are classified as carcinoma in situ (Tis), based on the American Joint Committee on Cancer, and are generally not thought to be capable of metastasis. The present study reports a rare case of lymph node metastasis in a 70-year-old female with Tis rectal cancer, who presented to Kangwon National University School of Medicine in December 2018. Although the tumor was confined to the mucosa without evidence of lymphovascular invasion, histopathological examination demonstrated metastasis to a regional lymph node. The patient underwent laparoscopic resection followed by concurrent chemoradiotherapy, and she has remained recurrence-free for the past 6 years. This case challenges the conventional understanding of Tis-stage colorectal cancer and highlights the need for the re-evaluation of lymph node involvement in early-stage cases. Further research is necessary to explore the mechanisms underlying lymph node metastasis in Tis rectal cancer.