In the history of thyroid cancer treatment, neck lymph node dissection is often inseparable from radical neck dissection. This surgery refers to the en bloc removal of lymphoid tissue in the neck and surrounding fat, muscle, nerves, blood vessels, etc. Also known as radical neck dissection, total neck dissection, radical neck dissection, etc.
Including radical neck dissection, functional (modified) neck dissection, selective lymph node dissection, and central lymph node dissection. At present, the most commonly used surgical procedures are central lymph node dissection and functional cervical lymph node dissection.
The lymphatic system is an important defense system in the human body. It is distributed all over the body and can produce killing factors and directly kill bacteria, viruses and even cancer cells. When there are cancer cells in human tissue, lymphocytes will gather around the cancer cells and engulf and kill the cancer cells. However, due to the heterogeneity of cancer cells, they have tenacious vitality and can survive even if they are swallowed by lymphocytes. Lymphocytes, on the other hand, sometimes circulate in the lymphatic system like blood cells. In this way, the lymphocytes, which were originally intended to kill cancer cells, became a convenient channel to help cancer cells spread. Like other tumors, thyroid cancer cells are prone to lymphatic metastasis, and the lymph nodes along the way become the transit point and shelter for cancer cells. Lymph nodes in the central region of the neck are often the first stop for metastases, with subsequent metastases to lateral neck and more distant lymph nodes. At this point, even if all the glandular tissue is removed, the cancer cells in the lymph nodes have already planted the seeds of metastasis and recurrence. Therefore, as lymphoid tissue is the most common site of metastasis, it is beyond reproach to perform lymph node dissection during lymph node dissection. It can detect scattered cancer cells as soon as possible, which helps to prevent metastasis as soon as possible. The lymph nodes are cleaned to minimize the recurrence and metastasis of cancer cells. The purpose of lymph node dissection is to completely remove sentinel sites where cancer cells may be lurking.
The lymph nodes in the neck are very rich. The American Joint Committee on Cancer divides the cervical lymph nodes into seven areas, which are of great significance for clinical diagnosis. It is basically demarcated by the vascular sheath of the carotid artery, the inner side of the carotid sheath belongs to the central area, and the outer side belongs to the lateral neck area. Lymph node dissection in the central region is a routine dissection, and even in relatively early stage thyroid cancer, the risk of occult metastases in the central region is higher. There are even about 30% to 50% of patients who did not find lymph node metastasis in preoperative or intraoperative examinations, but were found to have metastasis after postoperative pathology. Therefore, the domestic view is inclined to recommend ipsilateral prophylactic central lymph node dissection even if there is no lymph node metastasis in the preoperative assessment. But like follicular carcinoma, because it has very little chance of lymph node metastasis, routine dissection can be omitted.
The probability of lymph node metastasis in the lateral neck region is relatively low, and the surgical trauma is relatively large. If no metastasis is suspected, preventive lateral neck dissection is not recommended. It is currently recognized that lymph node dissection is only required if the preoperative examination is highly suspected or confirmed to have lateral neck lymph node metastasis. The thoroughness of neck lymph node dissection is very important for the prognosis of patients with thyroid cancer. The more thorough the dissection, the better the prognosis. Because lymph node dissection can reduce the chance of recurrence and metastasis of thyroid cancer, it can prolong the survival of patients. However, irregular dissection will not only increase the possibility of recurrence, but also bring considerable difficulty to the secondary operation and increase the chance of surgical complications.