Diagnosis criteria for colorectal cancer

Special staining and magnifying endoscopy have laid a material foundation for improving the diagnosis of colorectal cancer. However, we need to have a new understanding of changes in the morphology of lesions, such as unclear or disappeared vascular texture, red, rough, pale mucosa, interrupted innominate grooves, central depression of white spots around lesions, and mild deformation of the intestinal wall. These changes in concave and flat morphology must be taken seriously during endoscopic examinations. This is because the detection rate of canceration is higher and the degree of malignancy is higher in concave and flat types than in protruding colorectal tumors. Some data suggest [15] that flat tumors, i.e., Ⅱa, Ⅱb, and Ⅱc, may be cancer at the beginning. LST (laterally developed tumor) combined with colorectal cancer accounts for 8.4% to 52.5%. Benign LST can become cancerous within 3 years, while for protruding tumors, it takes about 5 to 10 years for adenoma to develop into cancer. Therefore, these changes in minor lesions should be treated as suspected cancer lesions and examined by staining endoscopy, or EUS examination should be performed for submucosal lesions.

Special stains

Staining of microlesion specimens can be divided into contrast method, staining method, pigment reaction method, and fluorescence method according to the type and mechanism of action of the pigment. The first three methods are the most commonly used. Before staining, the retention around the lesion should be completely aspirated and the area to be stained should be cleaned. Use lukewarm cleaning solution, because cold water can easily stimulate the mucosa, causing the mucosal folds in the lesion to contract and the intestinal peristalsis to increase, which is not conducive to observation; when flushing, the impact should be along the edge of the lesion so that the cleaning solution naturally forms a water flow to flush the lesion. Avoid directly impacting the lesion to induce bleeding and affect staining and observation. Usually 0.4% indigo carmine is used as a colorectal mucosal stain. Indigo carmine can mainly show the changes in the concave and convex of the mucosa. It is a non-mucosal absorption dye. When the staining effect is not ideal, it can be used repeatedly to obtain the best effect. However, before staining again, the dye on the mucosal surface should be rinsed clean.

Magnifying endoscope

The use of magnifying colonoscopy can achieve the purpose of distinguishing the fine structure of lesions, glandular morphology and even changes in cell structure. At present, general magnifying endoscopes can magnify images 200 times. The purpose of this magnifying endoscopic examination is to confirm the lesion by observing the type and changes of the glandular duct opening. It is close to histological diagnosis and is very helpful for the qualitative diagnosis of superficial lesions including Ⅱc lesions. The two newer colonoscopy techniques: en-docytoscope and endomicroscope, can respectively enlarge cells 1125 times and magnify endoscopic images 1000 times. The former can see the cell nucleus and cell structure, and the latter can see the cell and subcellular structure. Compared with the gold standard, the diagnostic rate of inflammatory bowel disease cancer is 90% accurate. However, the use of magnifying endoscopy alone is prone to miss the diagnosis of flat and shallow concave adenomas. Compared with raised lesions, this type of adenoma has an earlier time of canceration, a higher degree of malignancy, and a faster progression.