The types of colon cancer that exist

Medically reviewed by Neka Miller, PhD on June 6, 2021. To give you technically accurate, evidence-based information, content published on the Everlywell blog is reviewed by credentialed professionals with expertise in medical and bioscience fields.

Colon cancer remains one of the most common forms of cancer in the country. Excluding certain skin cancers, colon cancer is the third most common cancer in the United States (when breast and prostate cancers are combined). The lifetime risk of developing colon cancer hovers at just over 4 percent for everyone. It is also the third leading cause of cancer-related deaths in the United States.

The good news is that there is a wide range of treatments available to manage symptoms and control growth. When found early, such as through a colon cancer screening kit, colon cancer can be easily treated and cured. Understanding the different types of colon cancer can help you and your doctor determine the best mode of treatment.

Learn more about the different types of colon cancer below.

What is Colon Cancer?

Colon cancer broadly refers to any cancer that begins within the cells of the colon, also known as the large intestine. This is the last part of the digestive tract, right before the rectum. Because of that proximity and similar symptoms involved, cancers of the colon and the rectum are often grouped together (referred to as colorectal cancer).

Colon cancer typically starts as noncancerous lumps called polyps that form on the lining of the colon. When they are left untreated, polyps can eventually turn into malignant tissue. This development is slow (it can take 10 to 15 years for a colon polyp to develop into cancer), so most people with colon cancer experience no noticeable symptoms in the disease’s early stages.

Some common early signs of colon cancer include:

• Unexplained weight loss
• Persistent changes to your bowel habits, including diarrhea, constipation, or general changes to stool consistency
• Blood in your stools
• Rectal bleeding
• Feeling incomplete bowel emptying
• Persistent abdominal discomfort (pain, cramps, gas)
• Physical weakness and fatigue

These symptoms can vary based on the size of the tumor and its location within the large intestine.

Types of Colon Cancer

Colorectal cancers are identified by the type of cells they affect and the part of the colon or rectum that they start in.

Colorectal Adenocarcinoma

Adenocarcinomas in the colon and rectum are the most common type of colorectal cancer. They comprise about 95 percent of all colorectal cases, which means that if you are diagnosed with colon cancer, it’s likely an adenocarcinoma. “Adeno” means glands, while carcinoma refers to cancers that grow in epithelial cells, which are found in linings throughout the body. This means that adenocarcinomas are cancers that grow in the lining of the large intestine, usually starting in the inner lining before spreading to outer layers.

Within adenocarcinomas are two less common sub-types: mucinous adenocarcinomas and signet ring cell adenocarcinomas. Mucinous adenocarcinomas are made up of about 60 percent mucus. That large quantity of mucus may allow cancer cells to grow and spread more quickly, making them more aggressive than other adenocarcinomas. These comprise up to 15 percent of colorectal adenocarcinomas.

Signet ring cell adenocarcinomas are much rarer, accounting for less than one percent of adenocarcinomas. This type of cancer can be difficult to treat and highly aggressive.

Gastrointestinal Carcinoid Tumor

These tumors develop in neuroendocrine cells in the colon. Neuroendocrine cells are responsible for acting as receptors for neurotransmitters and for regulating hormone production. Gastrointestinal carcinoid tumors can also be grouped in with a type of cancer known as neuroendocrine tumors.

Gastrointestinal carcinoid tumors account for less than a percent of all colorectal cancer cases, though they are more common in other parts of the digestive system. Carcinoid tumors are slow-growing by nature, and aside from the gastrointestinal tract, they can grow in the lungs.

Primary Colorectal Lymphoma

This type of cancer develops in cells called lymphocytes, which make up the lymphatic system. Lymphocytes are a type of white blood cell that your immune system normally uses to combat infections.

While it typically starts in the lymph nodes, lymphoma in general can develop in numerous different parts of the body, like the bone marrow, spleen, and digestive tract. Primary colorectal lymphoma is extremely rare. It comprises about 0.5 percent of all colorectal cancer cases and about 5 percent of all lymphomas.

Gastrointestinal Stromal Tumors

Gastrointestinal stromal tumors (GISTs) also start in the walls of the gastrointestinal tract. Unlike adenocarcinomas, GISTs develop in special cells known as the interstitial cells of Cajal. These are the “pacemakers” of the GI tract, signaling when the GI tract muscles should contract to move food and liquids through the digestive system.

GISTs can develop anywhere in the digestive tract. About half of all GISTs start in the stomach. Most other cases occur in the small intestines. The rectum is the third most common location for GISTs, but they are otherwise extremely rare in the colon.

Leiomyosarcomas

Soft tissue sarcomas affect connective tissues, like muscles, fat, blood vessels, and deep skin tissues. While this type of cancer is not unheard of in the GI tract, it is extremely rare, particularly in the colon.

Leiomyosarcomas are cancers that start in smooth muscle cells. The colon and the rectum have three layers of these smooth muscle tissues, which work to move waste through your digestive tract. Leiomyosarcomas comprise about 0.1 percent of all colorectal cancer cases.

Diagnosing Colon Cancer

A professional diagnosis is the best way to determine the type of colon cancer that you may have, which can then determine the treatment options available. Tests and procedures for colon cancer screenings vary, but they usually start with a basic physical examination.

If your physical exam and present symptoms suggest colon cancer, your doctor may proceed with a blood test. No blood test can diagnose colon cancer on its own, but it can provide clues for your overall health, like your liver and kidney health, and eliminate other potential conditions. Colon cancers also sometimes produce a substance known as carcinoembryonic antigen (CEA). Regular tracking of CEA levels in your blood through colon cancer screenings can help your doctor determine your prognosis and the effectiveness of treatment.

A colonoscopy is one of the most common test procedures for colon cancer. This colorectal cancer screening involves the use of a long, slender, flexible tube that has a camera at its end. Inserted into your rectum, the scope can view your entire colon and rectum. Your doctor can even insert instruments into the colonoscope to remove colorectal polyps or take tissue samples for analysis and testing (biopsy).

Staging

Staging determines the extent and severity of cancer. This is essential to determining how much the cancer has grown as well as proper modes of treatment. For colon cancer, this can include imaging tests, like CT scans of the chest, abdomen, and pelvis. However, staging for colon cancer is usually determined following surgery.

Stages of colon cancer are determined by Roman numerals 0 to IV. The lower numbers denote that the cancer is relatively small and localized to the lining of the colon. Stage IV suggests that the cancer has spread to other parts of the body (metastasized).

If you think you may have some form of colon cancer, a good place to start is with the Everlywell home testing kit for colon cancer. For any patient that is experiencing bowel habit changes or is showing other common symptoms of colon or rectal cancer, our at-home screening kit is a great place to start when checking the health of their gastrointestinal tract.

This kit uses a fecal sample collection to detect blood in your stool, which can help to determine potential cancer in your colon. You can then take your results from your at-home colorectal cancer screening kit to your doctor to receive a more comprehensive diagnosis. Remember that the sooner you receive treatment, the better the outcome, so consider getting tested today to ensure your great health.