The goal of this observational study is to learn about the the pattern of metastasis of the No.253 lymph node in colorectal cancer. The main questions it aims to answer are: 1. What are the risk factors for metastasis to the No.253 lymph node? 2.What is the prognosis for patients with metastasis to the No.253 lymph node? Patients with descending colon cancer, sigmoid colon cancer, and rectal cancer who undergo curative surgery with dissection of the No.253 lymph node are included in this study

The No. 253 lymph node (also named as apical lymph node of inferior mesenteric artery), as the third station in the inferior mesenteric artery lymphatic system, plays a vital role in the lymphatic circulation of the descending colon, sigmoid colon, and rectum. They serve as the last barrier for tumor metastasis from regional to distant sites. The definition of the range of the No.253 lymph node primarily follows the Japanese Colorectal Cancer Treatment Guidelines: the medial boundary is the segment from the root of the inferior mesenteric artery to the origin of the left colic artery, the caudal boundary is from the origin of the left colic artery to the intersection with the inferior mesenteric vein, the lateral boundary is the outer margin of the inferior mesenteric vein, and the cranial boundary is from the horizontal section of the duodenum to the beginning of the jejunum. However, the pattern of metastasis of the No.253 lymph node in colorectal cancer remains unclear, with most studies being retrospective and showing significant differences in results. Therefore, the investigator plans to be the first internationally to carry out this retrospective, registry-based study to determine the metastasis pattern to the No. 253 lymph node in colorectal cancer. This will provide definitive clinical evidence for D3 lymph node dissection in colorectal surgery.

Inclusion Criteria:

1. Age: 18-75 years;
2. Underwent laparoscopic left hemicolectomy, sigmoid colectomy, or rectal cancer radical surgery.
3. Postoperative pathology confirmed as adenocarcinoma.
4. No evidence of distant metastasis.

Exclusion Criteria:

1. Previous history of malignant colorectal tumors.
2. Patients who have undergone multiple abdominal-pelvic surgeries.
3. Patients undergoing emergency surgery due to complications such as intestinal obstruction, intestinal perforation, or intestinal bleeding.
4. Surgery did not achieve R0 resection.
5. Patients with concurrent other malignant tumors or multiple primary colorectal cancers.
6. Patients unwilling to sign an informed consent or follow the study protocol for follow-up.

Patients with left-sided colorectal cancer (left colon cancer, sigmoid cancer, rectal cancer) underwent laparoscopic surgery with dissection of No.253 lymph node.