Clinical significance
1. Improve the accuracy of colorectal cancer staging
Surgical resection is the curative treatment for colorectal cancer. Surgery alone or combined with adjuvant therapy depends on the stage. Survival rate is high in low lymph node metastasis, and adjuvant chemotherapy (5-fluorouracil + tetrahydrofolate) is recommended for stage III patients. Adjuvant chemotherapy is not currently recommended for patients with negative lymph nodes [3]. As the survival rate of patients with “negative” lymph nodes should be relatively increased, however, 20-40% of them still die from metastatic disease [], so the current staging method may be inaccurate. There is no agreement on the optimal number of lymph nodes needed for accurate staging, and thus inadequate lymph node extraction or histologic analysis may be responsible for inaccurate staging. The conventional method for routine detection of lymph node status is to observe and evaluate each detected lymph node under light microscopy in a single section with HE staining, and although fat removal techniques can be used to increase the number of detected lymph nodes, adequate optimal lymph node extraction is still not guaranteed, and thus lymph node disease may be overlooked; at the same time, it is impractical to search for lymph node micrometastases in a large amount of lymph node tissue. Therefore, the conventional method of conventional lymph node detection may cause down-staging of colorectal cancer. Ren Hui, Department of Colorectal and Anal Surgery, Second Hospital of Jilin University
The need for accurate staging and the shortcomings of current methods have promoted the experimentation of SLN localization in colorectal cancer. The localization of sentinel lymph nodes is to identify those lymph nodes that are most likely to harbor metastases, and to improve the detection of lymph node micrometastases through serial sections of representative lymph nodes combined with immunohistochemical techniques, which Mulsow [2] (specifically) has shown to upregulate about 20%-40% of patients from stage I and II to stage III, and has important clinical implications for the prognosis and adjuvant treatment of colorectal cancer. It has important clinical significance for the prognosis and adjuvant treatment of colorectal cancer.
2. Detection of abnormal tumor lymphatic flow
Aberrant lymphatic drainage (ALD) is a condition in which lymph node localization reveals that the anterior lymph node is in an abnormal location for anatomical lymphatic drainage and is not included in the initial surgical field design. Local lymph node metastasis is one of the most important factors in the prognosis of colorectal cancer. However, approximately 20-40% of patients who invade the muscular layer of the intestinal wall without evidence of lymph node metastasis die from local recurrence. One possible explanation for this phenomenon is the occurrence of ALD in the tumor [8,15].
Lymph node localization studies have shown that the purely anatomical concept of lymphatic metastasis in colorectal cancer shows that the peri-intestinal lymph nodes are the first station of metastasis, followed by intermediate and proximal lymph nodes and then by more distant lymph nodes (e.g., para-abdominal aorta). The anterior lymph nodes can be located in unexpected locations, and abnormal lymphatic flow patterns in gastrointestinal tumors are not uncommon, and this has important prognostic implications. The difference between skip metastasis, which occurs in up to 10% of cases, and the concept of abnormal lymphatic flow in tumors? Lymph node localization studies have demonstrated that lymphatic flow can be directed from the tumor location to proximal or even para-aortic lymph nodes, which helps to explain the definition of skip metastasis. Even more surprisingly, anterior lymph nodes can be localized relatively far from the primary tumor [16].
Ectopic metastasis of lymph nodes in colorectal cancer may be associated with lymphatic reflux disturbances. SLN can detect the presence of abnormal tumor lymphatic flow intraoperatively or earlier while detecting the abnormal tumor lymphatic flow, thus avoiding missed diagnosis. Theoretically, SLN can improve the surgical effect of radical colorectal cancer surgery and increase the scope of radical lymphatic dissection [8, 16].
3. Discovery of micrometastasis (micrometastasis)
Micrometastasis is the deposition of microscopic tumor cells in the lymph nodes, usually ≤2 mm, located in the subperitoneal sinus of the lymph nodes, which proliferate in dependence on neovascularization. The histological significance is negative for HE staining and positive results for immunohistochemical testing. ［The clinical significance of [10] remains controversial, and it is unclear whether this is early metastatic disease or tumor metastasis captured by the body’s immune mechanisms; it is not known whether these deposits lead to local recurrence.
It is extremely expensive and impractical to perform these techniques on all resected lymph nodes. Also, routine pathology may miss isolated metastases, especially submicroscopic metastases. Colorectal cancer SLN localization techniques help pathologists to focus on 1 to 4 SLNs for detailed analysis by multilayer microsectioning, immunohistochemistry, and molecular techniques studies. Colorectal cancer SLN localization technique guides surgeons and histopathologists to find the lymph nodes most likely to hide micrometastases and helps one to understand the significance of micrometastases. [8, 9, 10]
In conclusion, although some hospitals in Europe and the United States have now applied the results of SLN detection for colorectal cancer in clinical practice, this technique is still in the research stage in most hospitals worldwide. Multicenter prospective studies on its accuracy and reliability are still continuing, and large samples of follow-up data are being analyzed to achieve consensus. As a hot topic in the field of colorectal cancer surgical treatment in recent years, sentinel lymph node localization and detection technology is becoming a major prognostic factor and has important guiding significance for the diagnosis and treatment of colorectal cancer.