1.How many layers of the intestinal wall are there? To understand the “intraepithelial neoplasia” on the colonoscopy report, we must first clarify the first question “How many layers of the intestinal wall are there?” Why do we need to know the stratification of the intestinal wall? Because simply speaking, if tumor cells are confined to the mucosal layer, it is called “intraepithelial neoplasia”; in other words, if tumor cells break through the mucosal layer and reach the submucosal layer, it is called “colorectal cancer”. Let’s have a brief understanding of how many layers of intestinal wall there are, the 4 layers are mucosal layer, submucosal layer, intrinsic muscle layer and plasma layer in order from inside to outside. The mucosal layer can be divided into three layers: mucosal epithelial layer, mucosal lamina propria and mucosal muscle layer. 2.What is intraepithelial neoplasia? ”Intraepithelial neoplasia” is a new term proposed by the World Health Organization (WHO) in 2000 and applied in the field of pathological diagnosis of colorectal tumors. As described above, intraepithelial neoplasia refers to the confinement of tumor cells to the mucosal layer. It should be reminded that, according to the pathological basis, intraepithelial neoplasia is a benign tumor of the large intestine. Why do you say so? The tumor cells in intraepithelial neoplasia are confined to the mucosal layer, but since there are no blood vessels and lymphatic vessels in the mucosal layer, just like the tumor cells lack a conduit to escape, lymph node metastasis and distant metastasis will not occur, so it is a benign tumor. By the same token, when the tumor cells break through the mucosal layer and reach the submucosal layer, because there are large blood vessels and lymphatic vessels in the submucosal layer, lymph node metastasis and distant metastasis may occur, which is a malignant tumor, that is to say, colorectal cancer is formed. The difference between intraepithelial neoplasia and colorectal cancer in the process of colorectal carcinogenesis is whether the tumor cells break through the mucosal layer. The main purpose of this regulation is to avoid clinicians to operate whenever they see cancer, which leads to excessive treatment and causes unnecessary harm to patients, and also to reduce the mental and psychological burden of patients, so as to avoid the “smell of cancer”. 3.Why do we need surgery? Why the pathology report of colonoscopy biopsy is intraepithelial neoplasia, but the doctor said it is colorectal cancer and needs to be operated? Does the possibility of surgery depend on the “intraepithelial neoplasia” in the colonoscopy report is really accurate? Intraepithelial neoplasia” is a pathological diagnosis, and whether it is accurate or not should be divided into two cases: 100% accurate: if the specimen sent for examination is a “complete resection specimen”, that is, “the whole tumor was cut down under the colonoscope and sent for examination”, then the diagnosis is basically 100% accurate. “Then the diagnosis is basically 100% accurate. Not 100% accurate: If the specimen sent for examination is a “partial specimen removed under the colonoscope”, i.e., “a few small pieces of the tumor are grabbed from the surface and sent for examination”, then the diagnosis is not so accurate. In fact, there are many cases of colon cancer that look very typical, but the pathology of colonoscopy biopsy is “intraepithelial neoplasia”. Studies have shown that patients diagnosed with intraepithelial neoplasia on preoperative colonoscopy biopsy have a 40-90% chance of being diagnosed with colorectal cancer after surgery. Why is the report “intraepithelial neoplasia”, but in fact “colorectal cancer”? 1. Biopsy tissue is too small: The biopsy forceps used for colonoscopy biopsy are very small, and a small piece of tissue “smaller than a sesame grain” is taken from the tumor. Therefore, it may not contain cancerous tissues, and no cancer cells can be found in pathological examination, so only “intraepithelial neoplasia” can be diagnosed. 2.The tumor is continuously changing, “tumor” cancer itself is a process from quantitative to qualitative change, or called “getting bigger first, then getting worse” process. “The “bad part” is very small at the beginning and often starts to grow from the center of the tumor, therefore, pathological biopsy sometimes cannot get the cancerous tissue. 3. Tumor cells “obscure” the intestinal wall stratification. In the small pieces of tumor tissues taken, the tumor cells may destroy the mucosal muscle layer (the last line of defense of the mucosal layer), so that the original intestinal wall stratification “changes from clear to blurred”. As a result, the pathologist is unable to determine whether the tumor has crossed the mucosal muscle layer and can only make the diagnosis of “high-grade intraepithelial neoplasia”. Therefore, the diagnosis of “intraepithelial neoplasia” in biopsy specimens according to the colonoscopy report is mostly colorectal cancer, which should not be taken lightly.