Colon cancer is any type of cancer that first grows in the colon, also known as the large intestine. Within this category, there are subtypes of tumors.
Colon cancer is any type of cancer that first grows in the colon, also known as the large intestine. It is a form of colorectal cancer, or cancer that beings in the rectum or colon. Within this broad category are several subtypes of tumors that can develop.
The most common type of colorectal cancer is adenocarcinoma. These tumors form in the cells lining the colon and rectum. According to the Cancer Treatment Centers of America, account for 95 percent of all colorectal cancer cases. Almost all colon cancers are adenocarcinomas. Surgery to remove adenocarcinomas is generally a very successful procedure.
There are also two uncommon subtypes of adenocarcinoma that can develop in the colon. Mucinous adenocarcinoma is made up of 50 percent mucus cells, which can cause the cancer to spread aggressively. These account for 10 to 15 percent of colorectal adenocarcinomas. Signet ring adenocarcinomas are rarer, making up less than one percent of adenocarcinomas. These are more aggressive than mucinous tumors and may be more difficult to treat.
When adenocarcinomas spread beyond the lining of the colon, they are known as invasive, or infiltrating, tumors. However, the American Cancer Society cautions that invasive colon cancer, with appropriate treatment, is not necessarily associated with a poorer prognosis than non-invasive cancer. Many factors that affect prognosis cannot be determined until tumor tissue is fully removed and examined by a medical pathologist.
Carcinoid tumors develop out of neuroendocrine cells, the cells that regulate hormone production in the body. As a result, these tumors can sometimes release hormone-like substances into the bloodstream.
For most people, the level of these hormones is not high enough to produce any symptoms. About 10 percent of those with carcinoid cancers, however, will experience carcinoid syndrome, which includes flushing of the skin, diarrhea, wheezing, and an elevated heart rate.
Two-thirds of all carcinoid tumors appear in the gastrointestinal tract, according to the Memorial Sloan Kettering Cancer Center. However, carcinoid tumors account for only about one percent of all colon cancers. They are often slow-growing and can take years to spread.
People with a family history of colon cancer or with stomach conditions that inhibit acid production have an increased risk for gastrointestinal carcinoid tumors. Most of these tumors are treated with surgery, though radiation or chemotherapies may be necessary as well if the cancer has spread.
Stromal tumors develop from the cells of the nervous system; when these form in the colon, they are known as gastrointestinal stromal tumors, or GISTs. They are much less common than adenocarcinomas or carcinoid tumors.
According to research published in the European Journal of Pathology, GISTs are most common in adults over age 50, and fewer than five percent of them develop in the colon. They are slightly more common in men than women. Most seem to develop sporadically, though some rare, inherited genetic conditions such as von Recklinghausen disease and Carney-Stratakis syndrome can increase your risk of GISTs.
Most of these tumors are benign and can be removed with surgery. In cases when gastrointestinal stromal tumors are not benign, researchers have found that these tumors respond well to chemotherapy drugs.
Rare types of colon cancers
Colorectal lymphomas develop in lymphocytes, a type of white blood cells that fight infection. Primary lymphoma tumors make up only 0.5 percent of all colorectal cancers and rarely develop in the colon.
Soft tissue sarcoma, another rare colorectal cancer, can develop in the smooth muscles that line the colon. Because the tissue where a sarcoma develops is elastic, the tumor can usually grow without producing symptoms. Sarcomas make up about 0.1 percent of all colon cancers.
Metastatic colon cancer
Metastatic colon cancer occurs when cells break away from a tumor in the large intestine. The cancer cells then spread to other parts of the body and settle, creating new tumors.
Though metastatic cancer can go anywhere, cancer cells from the colon most commonly spread to the liver. These tumors are generally removed with surgery. However, since metastatic cancer can be aggressive, follow-up treatment in the form of radiation or chemotherapy is often necessary as well.
Most colon cancers develop from growths in the lining of the large intestine known as adenomas or polyps.
Removing polyps is the best way to prevent colon cancer from developing, but polyps can only be detected with tests such as a colonoscopy or barium enema. Because tumors become more dangerous the longer they are left undiagnosed and untreated, it is important to see your doctor for regular colon cancer screening.
March 18, 2020
Christopher Nystuen, MD, MBA