Role of methylene blue in detecting the sentinel lymph node in colorectal cancer: In vivo vs. ex vivo technique

The identification of sentinel lymph nodes is a valuable oncological method, which aims at mapping lymphatic drainage and has the advantage of correctly staging the disease and assessing prognosis. Lymph node invasion is an important prognostic feature. In colorectal cancer, lymphadenectomy is not influenced by the positive or negative status of the sentinel lymph node. The identification of lymph nodes with possible invasion by staining the primary tumor with methylene blue can lead to improved staging and management. In other words, the consequent administration of neoadjuvant therapy (chemotherapy) to the appropriate patients may result in lower recurrence rates. Thus, the aim of the present study was to use methylene blue to identify the sentinel node/nodes in colorectal cancer and to determine whether the dye-capturing nodes were invaded by the tumor. This is a non-randomized prospective study, in which 26 patients with colon cancer with surgical indication were enrolled. Two types of methods were utilized: in vivo (16 patients) and ex vivo (10 patients). The identification rate was 75% for the in vivo technique and 60% for the ex vivo technique, resulting in a 69.26% overall identification rate. Of 18 patients with sentinel lymph nodes identified using dye, routine histological examination detected metastases in 6 (33.33%) of these patients. In conclusion, further research should be conducted into how the clinical application of sentinel node detection can be employed in colorectal cancer.