Case study: Mr. Li, 56, visited Mr. Fu’s clinic a while ago because of “irregular bowel movements, frequent bowel movements, but very little bowel movements”. After Mr. Fu personally performed a colonoscopy, he found a “large tumor” in the rectum, so a biopsy was taken from the surface of the “large tumor” and sent to the pathology department for a clear diagnosis. A few days later, Mr. Li, who got the pathology report, was relieved to see the diagnosis of “high-grade intraepithelial neoplasia”, not intestinal cancer, and happily went to see Director Fu for a follow-up. We recommend surgery or re-examination of colonoscopy to assess whether the tumor can be completely removed and then formulate the next treatment plan.” This confused Mr. Li – why is the colonoscopy biopsy pathology report “intraepithelial neoplasia”, but the doctor said it is colorectal cancer and recommended surgery? How many layers are there in the intestinal wall of the large intestine? To understand the “intraepithelial neoplasia” on the colonoscopy report, we must first clarify the first question – “How many layers are there in the intestinal wall of the colon?” Why do we need to know the stratification of the intestinal wall? Because simply speaking, if the tumor cells are confined to the mucosal layer, it is called “intraepithelial neoplasia”; in other words, if the 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 the intestinal wall are there? 4 layers From inside to outside, they are mucosal layer, submucosal layer, intrinsic muscle layer and plasma membrane layer. The mucosal layer can be divided into three layers: mucosal epithelial layer, mucosal lamina propria and mucosal muscle layer. (can be briefly understood) 2.What is intraepithelial neoplasia? “Intraepithelial neoplasia” is a new term proposed by World Health Organization (WHO) in 2000, which is 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 channel to escape, so lymph node metastasis and distant metastasis will not occur, which is a benign tumor; by the same token, when the tumor cells break through the mucosal layer and reach the submucosal layer, since there are larger blood vessels and lymphatic vessels in the submucosal layer, lymph node metastasis and distant metastasis may occur. The difference between intraepithelial neoplasia and colorectal cancer is whether the tumor cells break through the mucosal layer. The main purpose of this regulation is to prevent clinicians from operating on cancer, resulting in excessive treatment and causing unnecessary harm to patients, as well as 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”? The biopsy forceps used for colonoscopy biopsy are very small, and a small piece of tissue “smaller than a sesame seed” is taken from the tumor. Therefore, it may not contain cancerous tissues and no cancerous cells can be found in pathological examination, so only “intraepithelial neoplasia” can be diagnosed. 2.The tumor is changing continuously. “Tumor” cancer itself is a process of quantitative to qualitative change, or the process of “getting bigger first, then getting worse”. “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, according to the colonoscopy report, most of the biopsy specimens diagnosed as “intraepithelial neoplasia” are colorectal cancer, which should not be taken lightly. What should be done in this situation? If the tumor has general characteristics suggesting malignancy (i.e. “tumor” looks like malignant tumor), such as “large size (>2cm), no tip, bleeding ulcer on the surface, hard texture”, etc., we should highly suspect colorectal cancer to prevent misdiagnosis as benign and thus to prevent misdiagnosis as benign and thus delaying the treatment.