The most common type of colon cancer is adenocarcinoma, which usually has a favorable outcome if diagnosed and treated early. Screening is an important tool for a prompt diagnosis.
Colorectal cancer is the
Colorectal cancer, also called colon cancer, starts in the colon or rectum (the end of the GI tract) but can spread to other parts of the body. In many cases, the cancer will start as growths in the colon, called polyps. These are usually benign or noncancerous, but some may later become cancerous if left untreated.
Read on to learn more about the types of colon cancer and other conditions that may have similar symptoms or presentation.
The type of cancer someone has depends on the cells where it starts and will influence treatment options your healthcare professional or oncologist (cancer specialist) might suggest.
Adenocarcinoma
Adenocarcinoma is the most common type of colon cancer, accounting for
It may grow on the right side of the colon and can become large enough to cause pain and bleeding. This can lead to other symptoms like anemia caused by chronic blood loss.
Most adenocarcinomas start in polyps that grow in the colon, usually on the left side of the bowel. Polyps are typically benign or noncancerous, but some of them may turn into cancer if left untreated. This process can be long lasting and typically happens over several years.
The chance of
- Adenomatous polyps (adenomas): These polyps occasionally become cancerous.
- Hyperplastic polyps and inflammatory polyps: These polyps are more common, but they’re usually not precancerous. Some people with large (more than 1 centimeter) hyperplastic polyps might need colorectal cancer screening more often than usual. Screening methods may involve a colonoscopy or other imaging scans.
- Sessile serrated polyps (SSPs) and traditional serrated adenomas (TSAs): Just like adenomas, SSPs and TSAs have a high chance of developing into cancer if left untreated.
Adenocarcinoma subtypes
Adenocarcinoma is the most common type of colon cancer, but two subtypes of this cancer are rare and typically have a less favorable outcome:
- mucinous tumors, found in 10% to 15% of people with colon cancer
- signet ring tumors, which start in glandular cells
Sarcomas
A sarcoma is a type of cancer that can grow in blood vessels, muscles, and other connective tissues in the bowel or rectum. Sarcoma of the colon and rectum is rare.
Lymphomas
Lymphoma is a type of cancer that usually starts in the lymph nodes but can also start in the walls of the colon or rectum.
Other conditions may have similar symptoms to colon cancer. Symptoms of colon cancer may vary depending on how advanced the cancer is, but
- a change in bowel habits
- diarrhea
- constipation, or narrowing of the stool, which lasts for more than a few days
- the need to have a bowel movement but not feeling relieved afterward
- bleeding, typically bright red blood
- blood in the stool, which might make the stool look dark brown or black
- cramping or abdominal pain
- weakness
- fatigue
- unintended weight loss
The following table lists conditions that can have similar symptoms to colon cancer:
| Conditions | Similar symptoms |
|---|---|
| hemorrhoids | rectal bleeding |
| irritable bowel syndrome | changes in bowel habits, abdominal pain, bloating |
| inflammatory bowel disease | diarrhea, abdominal pain, rectal bleeding, weight loss |
| diverticulitis | abdominal pain, changes in bowel habits |
| ulcerative colitis | diarrhea, rectal bleeding, abdominal pain |
| Crohn’s disease | bowel inflammation, diarrhea, blood in stool, abdominal pain |
| bowel ischemia | abdominal pain, bloody stools |
Screening tests for diagnosing colon cancer include:
- fecal immunochemical test
- guaiac-based fecal occult blood test
- colonoscopy
- CT colonography (virtual colonoscopy)
- sigmoidoscopy
For people at higher risk of colon cancer or who present with a family history of the condition, screening for colon cancer may be necessary at a younger age. It’s important not to ignore symptoms.
If you think you may have colon cancer, contact a doctor or healthcare professional for advice. They can talk with you about the next steps.
Treatment options for colon cancer will depend on several factors, including:
- the type of cancer
- the stage of the cancer
- your specific circumstances
Some possible treatment options for colon cancer include:
- surgery
- radiotherapy (rectal cancer only)
- chemotherapy
- targeted drug therapy
- immunotherapy
Your healthcare professional or oncologist will discuss your options and recommend the treatment pathway that is most suitable for your needs. They’ll review possible side effects you might experience and consider your personal situation at every step.
Colon cancer is one of the most common cancers in the U.S. There are multiple types of colon cancer, but the most common is adenocarcinoma.
Adenocarcinoma typically has a favorable outlook if diagnosed and treated early, so it’s important to keep up with screening. Screening can involve certain procedures like a colonoscopy.
Certain conditions can present with similar symptoms to colon cancer, such as blood in the stool or abdominal pain. Contact your doctor or healthcare professional if you think you might have symptoms. They can evaluate your symptoms and rule out any serious condition.