What Is an Intestinal Polyp?

An intestinal polyp is an outgrowth or elevation of the intestinal mucosa. Intestinal polyps can be classified as neoplastic or non-neoplastic. Neoplastic polyps have the potential to become cancer, while non-neoplastic polyps are inflammatory, hyperplastic, or hamartomatous. In treating an intestinal polyp, its potential to progress to cancer and the symptoms of the patient are major considerations.

The formation of non-neoplastic types of polyps depends on the cause. Inflammatory polyps form due to recurrent abrasion and ulceration, leading to cyclical injury and healing. For instance, a polyp can form on the rectal mucosa due to the impairment of the relaxation of the anorectal sphincter, leading to the so-called solitary rectal ulcer syndrome.

Hyperplastic intestinal polyps are proliferations of the mucosa, and normally appear in people over the age of 50. Their cause is not fully understood, but it is believed that the cause is a decreased turnover and delayed shedding of epithelial 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 tissues located in a site where those tissues are normally located. When hamartomatous polyps occur with other symptoms, they cause what is called hamartomatous polyposis syndrome.

An example of a hamartomatous polyposis syndrome is Peutz-Jeghers syndrome, wherein the person has intestinal polyps mostly in the small intestine, colonic adenocarcinoma, and skin macules. There is an increased risk for breast, thyroid, lung, bladder, pancreatic, and gonadal cancers. Another example is familial adenomatous polyposis (FAP), an autosomal dominant disorder with the adenomatous polyposis coli (APC) mutation, wherein at least 100 polyps are present throughout the large intestine. Colorectal cancer will develop in patients who are left untreated.

Neoplastic polyp causes include carcinoid tumors, lymphomas, metastatic cancers, stromal tumors, and colonic adenomas. The most common and most important neoplastic polyp is the colonic adenoma, because it serves as the precursor lesion to most cases of colorectal adenocarcinomas, or colorectal cancer. Colorectal adenomas occur in as many as 50% of Western adults by the age of 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 earlier.

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 the risk of cancer. Colorectal adenomas less than 0.4 inch (1 cm) in size are usually benign, but studies suggest that 40% of polyps larger than 1.6 inches (4 cm) in diameter are cancerous.

Treating an intestinal polyp involves intestinal polyp removal or polypectomy, which uses electrocautery. Patients with polyps that are either too large or numerous may need laparoscopic surgery. When a patient has been diagnosed with a genetic syndrome, such as FAP, colon and rectum removal is the treatment option. This is called prophylactic proctocolectomy.