Colonic polyps mainly include colon polyps and rectal polyps, which are superfluous organisms of epithelial origin that are elevated in the mucosa of the large intestine. There are many ways to classify colorectal polyps, but Morson’s histological classification is widely used at home and abroad, which classifies colorectal polyps into four categories: tumorigenic, malignant, inflammatory and septic. The greatest advantage of this classification is that the tumor polyp which is closely related to carcinogenesis in colorectal polyps is collectively called adenoma, the relationship between misshapen polyp and carcinogenesis is unknown, and it is generally believed that carcinogenesis rarely occurs. In addition, polyps can be classified into long-tipped polyps, short-tipped polyps, broad-based polyps, hemispheric polyps and filiform polyps based on their general morphology. Since most colorectal polyps are asymptomatic, it is very difficult to evaluate their incidence accurately, so the detection rate is often used instead of the incidence rate. A total of 13,451 cases of fiberoptic colonoscopy were performed at PLA 150 Central Hospital, and 3,220 cases of colorectal polyps were detected, accounting for 16.4%, but the detection rate was less than 5% in a census of nearly 20,000 asymptomatic people, and about 75% of the polyps were seen in the elderly population over 60 years old.
Adenomas are true tumors of the mucosal epithelium of the large intestine, divided into tubular adenomas, villous adenomas and villous tubular adenomas. Patients with non-familial colorectal adenoma have a tendency to have multiple adenomas. About 50% of patients with adenoma have two or more adenomas, and 20-30% of patients have three or more adenomas, while tubular adenomas tend to be multiple and villous or villi tubular adenomas tend to be solitary. The degree of atypical hyperplasia of adenomas is commonly classified by the three-level classification proposed by Morson et al: mild atypical hyperplasia (grade I) is dominated by cytological heterogeneity, with a regular ductal or villous structure and good cell differentiation; moderate atypical hyperplasia (grade II) shows increased cellular heterogeneity and histological heterogeneity; severe atypical hyperplasia (grade III) shows both types of heterogeneity and significant glandular structure destruction. In recent years, quantitative DNA analysis and molecular biology techniques are of great value in grading the degree of atypical hyperplasia and identifying the cancer potential of adenomas.
Since colorectal polyps are often clinically asymptomatic, even if some gastrointestinal symptoms, such as bloating, abdominal pain, diarrhea and constipation, are mild and atypical, they can easily be overlooked. Therefore, anyone with unexplained blood in stool or digestive symptoms should pay attention to the hospital for further examination and confirmation of the diagnosis. The usual tests are fecal occult blood test, fiberoptic colonoscopy, radiological examination, and histopathological examination. Screening for adenoma patients focuses on those at high risk for adenoma, including: those with a personal or family history of intestinal adenoma or cancer; those over 40 years of age who have recently developed intestinal symptoms, especially blood in the stool; those with a family history of breast or endometrial cancer; and those with a history of colonic diverticula and gallstones.
Theoretical basis for the evolution of “adenoma-cancer”: biologically speaking, adenoma may be malignant from the beginning (i.e. Denovo direct theory), or it may undergo a process of malignant transformation. However, the “adenoma-cancer” theory of development has been generally agreed upon by scholars. Nevertheless, carcinoma is not an inevitable outcome for all adenomas; in fact, the majority of adenomas do not become cancerous throughout life; moreover, it takes 5-15 years for a colorectal adenoma to develop into colorectal cancer. The risk factors for adenoma cancer are mainly as follows: 1. size of adenoma: the general rule is that the chance of adenoma cancer increases with the increase of adenoma volume, large adenoma is prone to cancer, the cancer rate of adenoma less than 1.0cm does not exceed 1.5%, the cancer rate of polyp greater than 2cm reaches 30%-50%. 2. shape of the tip: generally adenoma with long tip is rarely carcinogenic. The number of adenomas: the chance of cancer is higher for multiple adenomas than for single adenomas. 4. age and gender: the risk of adenoma cancer increases with age, from 2% before the age of 50 to 15.3% after the age of 70; from the gender factor, the rate of adenoma cancer is higher for women than for men. 5. location of adenoma: the rate of adenoma cancer in rectum is 7.3%, while the rate of adenoma cancer in sigmoid colon is 7.3%. The rate of adenoma of rectum is 7.3%, while the rate of adenoma of sigmoid colon is 24.8%.6. The amount of histological villous component: villous adenoma is easy to become cancerous, while the rate of tubular adenoma is low. In the tertiary classification, the incidence of cancer was 5.7%, 18.0% and 34.5% for adenoma with mild, moderate and severe atypical hyperplasia, respectively. Choroidal adenomas are often associated with grade III atypical hyperplasia and are prone to carcinogenesis.
In summary, colorectal polyps are a relatively common colorectal disease, polyp cancer is only a very small number. Among them, the diagnosis and treatment of tumor polyp (adenoma) has become one of the important topics in the prevention of colon and rectal cancer.