Colorectal cancer can occur without polyps, but it is thought to be an uncommon event. Individuals with long-standing inflammatory bowel diseases, such as chronic ulcerative colitis and Crohn's colitis, are at increased risk for developing colorectal cancer that occurs in the absence of obvious polyps.
No. Some abnormal growths can actually be benign. And there are several different kinds of colon polyps. Not all of them will turn into cancer.
Overview. A colon polyp is a small clump of cells that forms on the lining of the colon. Most colon polyps are harmless. But over time, some colon polyps can develop into colon cancer.
Polyps are common in American adults, and while many colon polyps are harmless, over time, some polyps could develop into colon cancer. While the majority of colon cancers start as polyps, only 5-10% of all polyps will become cancerous.
It takes approximately 10 years for a small polyp to develop into cancer. Family history and genetics — Polyps and colon cancer tend to run in families, suggesting that genetic factors are important in their development.
Adenomas: Many colon polyps are the precancerous type, called adenomas. It can take seven to 10 or more years for an adenoma to evolve into cancer—if it ever does. Overall, only 5% of adenomas progress to cancer, but your individual risk is hard to predict.
If your doctor finds precancerous polyps, there is no need for any additional treatment as long as they remove the entire polyp. Removing the tissue stops the development of cancer.
If your doctor finds one or two polyps less than 0.4 inch (1 centimeter) in diameter, he or she may recommend a repeat colonoscopy in 7 to 10 years, depending on your other risk factors for colon cancer. Your doctor will recommend another colonoscopy sooner if you have: More than two polyps.
Colon cancers develop from precancerous polyps that grow larger and eventually transform into cancer. It is believed to take about 10 years for a small precancerous polyp to grow into cancer.
A gastroenterologist, the specialist who usually performs a colonoscopy, can't tell for certain if a colon polyp is precancerous or cancerous until it's removed and examined under a microscope.
When the carcinoma spreads to the submucosa, the polyp is considered to have become malignant, being able to spread to lymph nodes or distant sites. The tumors that affect the submucosa are classified as T1 and correspond to Stage I of the TNM staging system.
They can occur anywhere in the large intestine or rectum, but are more commonly found in the left colon, sigmoid colon, or rectum.
Smoking, obesity, diabetes, and inadequate exercise are risk factors for polyps, but many people with none of these risk factors have precancerous polyps in the colon. There are genetic risk factors for developing polyps as well.
Colorectal cancer can occur without polyps, but it is thought to be an uncommon event. Individuals with long-standing inflammatory bowel diseases, such as chronic ulcerative colitis and Crohn's colitis, are at increased risk for developing colorectal cancer that occurs in the absence of obvious polyps.
Colorectal cancer can occur in young adults and teenagers, but the majority of colorectal cancers occur in people older than 50. For colon cancer, the average age at the time of diagnosis for men is 68 and for women is 72. For rectal cancer, it is age 63 for both men and women.
Figure 1 shows the cumulative incidence of colorectal cancer starting 1 year after a negative colonoscopy: 0.4% at 3 years, 0.8% at 5 years and 2.3% at 10 years. The overall incidence rate of colorectal cancer was 1.8/1,000 person-years in the study cohort.
Colon cancer is typically slow-growing, starting as a benign polyp that eventually becomes malignant. This process may occur over many years without producing any symptoms. Once colon cancer has developed, it may still be years before it is detected.
So, the more polyps you have, the higher your cancer risk. Someone with just one or two small polyps is generally at lower risk of having or developing colon cancer than someone with three to nine, or more.
Most polyps found during a colonoscopy can be removed safely and effectively during the procedure. In some cases, however, a colonoscopy can reveal that there are polyps too large to safely remove. These are complex polyps, which make up about 10-15% of all polyps, and usually require additional procedures to remove.
Research indicates that as many as 60 percent of polyps may grow back within three years. Also, about 30 percent of patients who've had polyps removed will develop new ones. This is why it is important to talk to the care team about follow-up screening within five years after the polyps are removed.
If a doctor discovers polyps, they will often remove them via a colonoscopy or laparoscopy. The doctor will then send any removed polyps to a pathologist for a biopsy to see if cancer is present. If the biopsy reveals that cancer is present, then cancer specialists will outline a treatment plan for the person.
Depending on their size and location in the colon, serrated polyps may become cancerous. Small, serrated polyps in the lower colon, also known as hyperplastic polyps, are rarely malignant. Larger serrated polyps, which are typically flat (sessile), difficult to detect and located in the upper colon, are precancerous.