Colorectal cancer is cancer that starts in the rectum or colon. The cancer can be called rectal or colon cancer, depending on where it begins. Rectal cancer and colon cancer are typically grouped because of the many features they have in common. Rectal and colon cancer symptoms can include:
- Blood in the stool or rectal bleeding
- Change in the bowel habits (including constipation, diarrhea, or change in stool consistency)
- Abdominal discomfort that is persistent (gas, pain, or cramps)
- Fatigue or weakness
- Unexplained weight loss
Many patients won’t experience colon cancer symptoms in the early stages. However, if you suspect you have the condition or you notice one or more of the symptoms, visit your doctor right away.
Understanding Colorectal Cancer
Most colorectal cancers begin as a growth on the rectum or the inner lining of the colon. The growths are also known as polyps. Some of the growths can turn into cancer. However, not all polyps can become cancerous. The possibility of a polyp becoming cancerous will depend on the type of polyps. Below are the different types of polyps:
- Traditional serrated adenomas or TSA and sessile serrated polyps or SSP. These types of polyps are typically treated similar to adenomas since they have a much higher risk of colorectal cancer.
- Inflammatory polyps and hyperplastic polyps. These two polyps have many things in common. However, generally, they are not pre-cancerous. Those with more than 1 cm hyperplastic polyps might be required to have colorectal cancer screening more frequently.
- Adenomatous polyps (also known as adenomas). At times, adenomas can turn into cancer so they are sometimes referred to as pre-cancerous condition. There are three types of adenomas: villous, tubular, and tubulovillous.
There are certain factors that can increase an individual’s risk. Some of the most common include:
- If the polyp found is larger than 1 cm
- If there are more than 3 polyps found
- If the polyp removed has dysplasia
How the Condition Spreads
If the cancer starts in the polyps, over time, it can grow into the rectum or colon walls. The colon and rectum’s walls are made up of several layers. Colorectal cancer begins in the mucosa (or the innermost layer). Eventually, it either grows outward through all or some of the layers.
When the cancer cells are present in the walls, they can turn into lymph or blood vessels. The cancer cells can also travel to the other distant parts of the body like the lymph nodes. The extent of the spread (or the cancer stage) will depend on how deep it has grown into the walls or if the cancer has spread to the rectum or colon.
Cancer in the Rectum and Colon: Different Types
Colorectal cancers are mostly adenocarcinomas. Certain adenocarcinoma subtypes like the mucinous and signet ring have a worse outlook (or prognosis) compared to the other adenocarcinoma subtypes.
- Sarcomas. This type can begin in the muscle layers, blood vessels, or the connective tissues found in the walls of the rectum or colon. Sarcomas of the rectum or colon are considered rare.
- Carcinoid Tumors. This type begins from the hormone-making cells found in the intestine.
- Lymphomas. This is known as the cancer of the cells of the immune system. Typically, this type starts in the lymph nodes. However, they can also begin in the rectum, colon, and other organs.
- Gastrointestinal Stromal Tumors (GISTs). This type begins in the colon’s walls known as the interstitial cells of Cajal. Some of the tumors can be benign (meaning, not cancerous). The tumors are also typically found in the digestive tract. However, it’s very rare that they develop in the colon.
