In China, the 5-year survival rate of colorectal cancer patients after surgery still hovers around 50%. One of the reasons is that the lack of attention to tumor-free technique during surgical operation leads to dissemination of cancer cells, resulting in local recurrence, implantation or metastasis after surgery.

Principle of non-extrusion
Surgery for malignant tumors emphasizes the need to move gently during surgery and pay attention to breaking veins before arteries when breaking blood vessels, so as to prevent tumor cells from spreading along blood vessels and lymphatic vessels.

Principle of sharp dissection
Surgery for malignant tumor is relatively large and high risk, avoiding blunt tearing can reduce bleeding and injury. The requirement of performing surgery under sharp dissection is not only for the cleanliness of the surgical picture, but also for the need of surgical safety as required by the principle of tumor-free surgery for malignant tumors.

Principle of isolation
The principle of tumor isolation simply means to separate cancerous tissue from normal tissue to reduce implantation, but in practice there are many details to pay attention to. For example, when the benign or malignant nature of the tumor cannot be clarified, it should be put into the bag and removed by rotary cutting.

Principle of reducing intraoperative spread
In order to reduce intraoperative spread, firstly, the order of surgical operation should be paid attention to:
Free the tumor from the tumor site
Ligation of veins at the root of the tumor first
Then deal with arteries and lymphatic vessels
Block intraoperative hematogenous metastasis of tumor cells

Principle of block resection
Complete resection of the cancerous lesion and the subclinical lesions around the cancerous lesion is also the theoretical basis of surgery for malignant tumors. For cystic, suspected malignant tumors, surgery should emphasize the integrity of the peritumor to reflect anaplastic surgery.

Principle of reducing cancer cell contamination
The principle of reducing the contamination of cancer cells mainly refers to avoiding the shedding of cancer cells and planting them in the surgical trauma, and even exposure to the pelvic and abdominal cavities should be avoided. Therefore, care should be taken to avoid blood outflow to contaminate the surgical area during peri-cancer dissection.