[Sentinel lymph node mapping in colorectal and anal tumors from the beginning until now]

Sentinel lymph node biopsy in colorectal cancer remains controversial. Lymph node metastasis is the most important prognostic factor, and even in the absence of lymph node metastasis, the risk of local recurrence is 15-20%.

The sentinel lymph node was identified in vivo by subserosal injection of blue dye or indocyanine green (ICG), and ex vivo by submucosal or subserosal injection. Stained lymph nodes were examined by the pathologist conventionally with hematoxylin-eosin staining, and in cases of negativity, with serial sectioning and immunohistochemistry and/ or RT-PCR.

Despite the high detection rate of 70-99%, sensitivity for macrometastasis is low (33-93.1%), but improves with the detection of micrometastasis. Stage migration based on micrometastasis detection ranged between 5-15%. Aberrant lymphatic drainage occurs in 3.9-7.1% of cases.

At present, the sensitivity of colorectal sentinel lymph node identification is not suitable for guiding treatment, as the false negative rate is high. This is due to the lack of standardization, inadequate patient selection, and the large number of T3-4 stage tumors. Several authors recommend investigating early T1-2 stage tumors, the incidence of which is increasing due to screening.