Intestinal cancer is cancer that develops anywhere in the small or large intestine. The term covers two very different categories: colorectal cancer, which is the fourth most common cancer in the United States with an estimated 158,850 new cases in 2026, and small intestine cancer, which is comparatively rare at roughly 14,450 new cases per year, representing just 0.7% of all new cancer diagnoses. Because the intestines span a large stretch of the digestive tract, the specific type, behavior, and outlook of the cancer depends heavily on where it starts and what kind of cell it grows from.
Large Intestine vs. Small Intestine Cancer
The large intestine (colon and rectum) is the far more common site. Colorectal cancer typically begins as small growths called polyps on the inner lining, some of which can turn cancerous over years. This slow progression is exactly why screening is so effective: catching and removing polyps before they become malignant can prevent cancer entirely.
Small intestine cancer behaves differently. The small bowel is actually longer than the colon, yet cancer develops there far less often. Scientists believe this is partly because food moves through the small intestine faster, reducing the time that the lining is exposed to potential carcinogens. Small intestine cancers also tend to be harder to detect because the organ is difficult to reach with standard scopes.
Types of Intestinal Cancer
Cancers are classified by the type of cell they grow from, and the intestines contain several different cell types.
- Adenocarcinoma starts in the glandular cells that line the intestinal wall. It is the dominant type in the colon and rectum and accounts for about one-third of small intestine cancers.
- Carcinoid tumors grow from hormone-producing cells that help regulate digestive juices. These neuroendocrine tumors make up just under half of all small intestine cancers and tend to grow more slowly than adenocarcinomas.
- Lymphoma originates in immune cells within the intestinal wall. It can occur in either the small or large intestine.
- Sarcoma develops in connective tissues like muscle or cartilage within the intestinal wall. These are the least common.
Colorectal cancer is almost always adenocarcinoma, which is why treatment guidelines for it are more standardized. Small intestine cancer is split more evenly among different cell types, so the treatment approach varies more from patient to patient.
Common Symptoms
Many people with intestinal cancer have no symptoms in the early stages. When symptoms do appear, they depend on the size of the tumor and its location. For colorectal cancer, common signs include a persistent change in bowel habits (more frequent diarrhea or constipation), rectal bleeding or blood in the stool, ongoing abdominal cramps or pain, a feeling that the bowel doesn’t fully empty, unexplained weight loss, and fatigue or weakness.
Small intestine cancer can cause similar abdominal pain and weight loss, but may also lead to nausea, bloating, or a partial blockage of the intestine as the tumor grows inward. Carcinoid tumors sometimes trigger flushing or diarrhea by releasing excess hormones, though this is more common once the cancer has spread to the liver.
The overlap between these symptoms and everyday digestive problems is one reason intestinal cancers often go undetected until they’ve progressed. Persistent symptoms lasting more than a few weeks, especially unexplained bleeding or weight loss, warrant investigation.
Risk Factors
Some risk factors apply broadly to intestinal cancer, while others are specific to colorectal or small bowel disease.
Two inherited genetic conditions stand out. Lynch syndrome is the most common hereditary colorectal cancer syndrome, accounting for roughly 3% of all new colorectal cancer diagnoses. It results from inherited mutations in genes responsible for repairing DNA errors, which allows damaged cells to accumulate faster. Familial adenomatous polyposis (FAP) causes hundreds to thousands of polyps to develop in the colon and rectum, usually starting in the teenage years. People who inherit the gene variant responsible for FAP have a greater than 90% chance of developing colon polyps, and without intervention, cancer becomes nearly inevitable.
Beyond genetics, chronic inflammatory bowel disease (particularly longstanding Crohn’s disease affecting the small intestine or ulcerative colitis in the colon) raises risk over time. Lifestyle factors also play a role: diets high in processed meat, obesity, smoking, and heavy alcohol use are all linked to higher colorectal cancer rates. Age is the single biggest non-genetic risk factor, with incidence climbing sharply after 45.
How Intestinal Cancer Is Diagnosed
For the colon and rectum, colonoscopy remains the gold standard. A flexible, lighted tube is passed through the entire colon, allowing a doctor to both see and remove abnormal growths in real time. Most patients receive sedation, and the procedure requires thorough bowel preparation the day before. If a polyp or suspicious area is found, it’s removed or biopsied during the same procedure.
When a full colonoscopy isn’t possible or is incomplete, alternatives include sigmoidoscopy (which examines only the lower portion of the colon) and CT colonography, sometimes called virtual colonoscopy. CT colonography uses special X-ray equipment to build detailed images of the colon from outside the body. It still requires bowel prep, and if anything abnormal shows up, a standard colonoscopy is needed to remove it.
The small intestine is harder to visualize. Capsule endoscopy, where you swallow a pill-sized camera that transmits images as it travels through your digestive tract, is one option. The camera takes thousands of pictures and sends them to a small recorder worn on your body. The capsule eventually passes naturally. This technique is currently approved for people with incomplete colonoscopies or suspected bleeding, not as a routine screening tool.
CT scans and MRI of the abdomen help determine whether cancer has spread beyond the intestinal wall to lymph nodes or distant organs like the liver.
Staging and What It Means
Once diagnosed, intestinal cancer is staged to describe how far it has spread. Staging uses three factors: the depth of the tumor in the intestinal wall, whether nearby lymph nodes are involved, and whether the cancer has reached distant organs.
A tumor confined to the inner lining is the earliest stage. As it grows deeper through the muscle layers and eventually penetrates the outer wall, the stage increases. If cancer cells reach one or two nearby lymph nodes, that’s considered regional spread. Three or more involved lymph nodes signals more extensive regional disease. Distant metastasis, often to the liver or the lining of the abdominal cavity, marks the most advanced stage.
For small intestine adenocarcinoma, the five-year survival rate is 86% when the cancer is still localized to the intestinal wall, 80% when it has spread regionally, and 47% when it has reached distant organs. These numbers, based on patients diagnosed between 2015 and 2021, reflect averages across all ages and health conditions.
Treatment Options
Surgery is the primary treatment for intestinal cancer that hasn’t spread widely. The goal is to remove the section of intestine containing the tumor along with a margin of healthy tissue and nearby lymph nodes. For many early-stage cancers, surgery alone can be curative.
Chemotherapy is commonly added after surgery for colorectal cancers that have reached the lymph nodes (stage 3) or beyond. Treatment typically involves a combination of drugs given in cycles over several months. For advanced disease, chemotherapy may also be used to shrink tumors before surgery or to control cancer that can’t be surgically removed.
Immunotherapy has become an important option for a subset of colorectal cancers. Tumors with specific genetic features, particularly those linked to DNA repair problems (the same mechanism behind Lynch syndrome), can respond dramatically to immunotherapy drugs that help the immune system recognize and attack cancer cells. Not all intestinal cancers qualify, so genetic testing of the tumor is now a standard part of treatment planning.
Targeted therapies work by blocking specific molecules that help cancer cells grow or spread. These are mainly used in advanced colorectal cancer and are chosen based on the genetic profile of the individual tumor.
Screening and Prevention
The U.S. Preventive Services Task Force recommends that adults at average risk begin colorectal cancer screening at age 45. Several screening methods are available, from stool-based tests done at home to colonoscopy. The best screening test is the one you actually complete, and your choice may depend on availability, comfort, and how often you’re willing to repeat it (stool tests are done more frequently, while colonoscopy is typically repeated every 10 years if results are normal).
People with hereditary syndromes like Lynch syndrome or FAP need screening strategies that start much earlier and occur more frequently than standard guidelines. If you have a parent or sibling diagnosed with colorectal cancer, especially before age 50, earlier and more intensive screening is generally recommended.
There is no established routine screening program for small intestine cancer due to its rarity and the difficulty of accessing the small bowel. Surveillance in high-risk individuals, such as those with Crohn’s disease affecting the small intestine, is handled on a case-by-case basis.