Intestinal polyps can be neoplastic or non-neoplastic and may become cancerous. Inflammatory, hyperplastic, and hamartomatous polyps have different causes and risks. Colon adenoma is the most common malignant polyp and can lead to colorectal cancer. Treatment involves removal, and prophylactic proctocolectomy may be necessary for genetic syndromes.
An intestinal polyp is an outgrowth or elevation of the intestinal lining. Intestinal polyps can be classified as neoplastic or non-neoplastic. Neoplastic polyps have the potential to become cancerous, while nonneoplastic polyps are inflammatory, hyperplastic, or hamartomatous. In the treatment of an intestinal polyp, its potential for progression to cancer and the patient’s symptoms are important considerations.
The formation of non-cancerous types of polyps depends on the cause. Inflammatory polyps form due to recurring abrasion and ulceration, leading to cyclic injury and healing. For example, a polyp can form on the rectal mucosa due to impaired relaxation of the anorectal sphincter, leading to the so-called solitary rectal ulcer syndrome.
Hyperplastic intestinal polyps are growths of the mucosa and usually appear in people over the age of 50. Their cause is not fully understood, but the cause is thought to be reduced turnover and a delay in the spread of skin cells. Hyperplastic polyps do not progress to cancer.
The causes of hamartomatous polyps are mainly genetic or acquired. Hamartoma refers to a tumor-like growth of mature tissue located at a site where those tissues are normally found. When hamartomatous polyps occur with other symptoms, they cause what is called hamartomatous polyposis syndrome.
An example of hamartomatous polyposis syndrome is Peutz-Jeghers syndrome, in which the person has intestinal polyps mainly in the small intestine, colon adenocarcinoma, and skin macules. There is an increased risk of breast, thyroid, lung, bladder, pancreatic and gonadal cancers. Another example is familial adenomatous polyposis (FAP), an autosomal dominant mutational disease of adenomatous polyposis coli (APC), in which at least 100 polyps are present throughout the large intestine. Colorectal cancer will develop in untreated patients.
The neoplastic causes of polyps include carcinoid tumors, lymphomas, metastatic tumors, stromal tumors, and colonic adenomas. The most common and most important malignant polyp is colon adenoma, because it serves as a precursor lesion to most cases of colorectal adenocarcinomas or colorectal cancer. Colorectal adenomas occur in as many as 50% of Western adults by age 50, which is why colonoscopy screening is recommended by age 50. When a person has a relative who had colon cancer at an early age, screening should be done first.
Most colorectal adenomas are benign, but some people may already have invasive cancer when they are detected. Size is the most important factor associated with cancer risk. Colorectal adenomas smaller than 0.4 inch (1 cm) are usually benign, but studies suggest that 40 percent of polyps larger than 1.6 inch (4 cm) in diameter are cancerous.
Treatment of an intestinal polyp involves removal of the intestinal polyp or polypectomy, which uses electrocautery. Patients with polyps that are too large or numerous may need laparoscopic surgery. When a patient has been diagnosed with a genetic syndrome, such as FAP, removal of the colon and rectum is the treatment option. This is called a prophylactic proctocolectomy.
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