Small Intestine Cancer Diagnosis and Staging

November 22, 2024

This page was reviewed under our medical and editorial policy by Laleh Melstrom, M.D., M.S., associate professor of surgery and immuno-oncology, Division of Surgical Oncology, Department of Surgery, City of Hope^® Cancer Center Duarte

Several tests are necessary to make a small intestine cancer diagnosis and learn more about the stage of the disease when discovered.

Small intestine cancer, sometimes called small bowel cancer, has different forms, depending on the type of cell in which it begins. The information here applies to small intestine adenocarcinoma, which arises in the gland cells that line the inside of the intestine. It is the most common form of small intestine cancer, accounting for about one-third of cases.

How Is Small Intestine Cancer Detected and Diagnosed?

Small intestine cancer is usually diagnosed after symptoms prompt a visit to the doctor. However, the symptoms and signs of the cancer, such as abdominal pain and blood in the stool, may be caused by numerous (and far more common) conditions. Various tests are needed for a definitive diagnosis.

In general, the diagnostic process begins with the doctor taking a medical history — asking about symptoms, existing medical conditions, family history and potential risk factors for small intestine cancer. The doctor also performs a physical exam, looking for signs such as swelling in the abdomen or sounds that indicate a possible blockage in the intestine.

Tests for Small Intestine Cancer

Testing for small intestine cancer may involve blood work, imaging and exploratory procedures, including the following.

Blood tests: Small intestine cancer often causes intestinal bleeding, which may result in low red blood cell levels (anemia). Blood tests are able to detect low red blood cell levels, as well as abnormal levels of certain substances released by the liver and other tissues, that may suggest cancer is present.

Other tests allow doctors to examine the lining of the small intestine directly. However, it is important to note that the common screening test, colonoscopy, is unable to detect small intestine adenocarcinoma because that procedure examines only the colon and rectum (the large intestine).

Endoscopy: This procedure allows the doctor to search for abnormal-looking tissue in the upper digestive tract without making an incision. It may be performed in the ways listed below.

• Upper endoscopy: Here the doctor uses an endoscope, a thin, flexible tube outfitted with a tiny video camera. It is inserted into the mouth and guided through the throat and stomach to the first part of the small intestine. If any abnormalities are seen, tissue samples may be removed for viewing under a microscope.
• Double-balloon enteroscopy: This procedure may be necessary if the doctor needs to delve deeper into the small intestine (which is roughly 20 feet long). It uses a special instrument that contains two tubes, one inside the other. The inner tube, an endoscope, is moved a short distance into the intestine, then a balloon at its tip is inflated to hold the scope in place. Next, the outer tube is advanced to reach the end of the endoscope; a balloon at its tip is inflated to secure it in place. Those steps are repeated many times to gradually move the endoscope through the length of the intestine.
• Capsule endoscopy: This procedure skips the scope altogether. Instead, the patient swallows a capsule that contains a light and tiny wireless camera. The camera takes thousands of pictures as it moves through the digestive tract, sending the images to a recorder worn over the shoulder or around the waist. The capsule is eventually expelled during a bowel movement.

Certain scans may be useful in detecting small intestine cancer or in showing whether it has spread or is causing problems, such as an intestinal obstruction.

Barium X-ray: These specialized X-rays use barium, a silver-white metallic compound, to help highlight tissue abnormalities. The patient either drinks a liquid containing barium (barium swallow test) or receives it via a tube inserted through the mouth or, sometimes, the anus. X-rays are taken as the barium moves through the digestive tract. This test is performed less often now than in years past due to the availability of endoscopy.

Computed tomography (CT) scan: A CT scan generates detailed images of the body’s soft tissues. Tumors in the small intestine may not show up well on a CT scan, but the scans may be helpful in other ways, such as gauging whether a diagnosed small intestine cancer is spreading.

Magnetic resonance imaging (MRI) scan: An MRI scan also creates detailed images of soft tissues, but uses strong magnets and radio waves instead of X-rays. It may be useful in assessing suspected small intestine cancer, but it is performed less often than CT scan, which is a simpler procedure.

Biopsy: While endoscopy and, to a lesser extent, imaging are able to find areas of tissue that appear abnormal, only a biopsy is able to diagnose small intestine cancer. Biopsied tissues are examined under a microscope for cancer. The tissue sample is often taken during an endoscopy, but in some cases, surgery is necessary.

Small Intestine Cancer Stages

Small intestine cancer is typically given a clinical stage at the time of diagnosis, based on the tests detailed above. In cases where a patient has undergone surgery, the cancer may also be given a pathological (or surgical) stage. Staging describes the extent of the cancer, including how deeply it has grown into the intestinal wall and whether it has spread beyond the intestine.

The small intestine wall has multiple layers, listed below.

Mucosa: This is the innermost layer, composed of a membrane called the epithelium, connective tissue and a thin layer of muscle.

Submucosa: This fibrous tissue surrounds the mucosa.

Muscularis propria: This is a thick muscular layer that contracts to push food through the digestive tract.

Subserosa and serosa: These thin layers of connective tissue form the outermost part of the intestinal wall.

TNM Staging

The official staging system for small intestine adenocarcinoma is known as TNM.

T refers to the size and location of the main tumor.

N describes whether the tumor has spread to nearby lymph nodes.

M refers to whether the cancer has metastasized to distant parts of the body.

Using those three factors, doctors group small intestine adenocarcinoma into the following stages.

Stage 0: The cancer is only in the epithelium, and has not spread to nearby lymph nodes or other areas of the body.

Stage 1: The tumor has grown deeper into the mucosa or passed into the submucosa or muscular layer of the intestine, but has not spread to lymph nodes or distant sites.

Stage 2a: The cancer has grown through the muscular layer into the subserosa, but not beyond the intestine.

Stage 2b: The cancer has reached the serosa (outermost layer), but is still confined to the intestine.

Stage 3a: The cancer has spread to one or two nearby lymph nodes.

Stage 3b: The cancer has spread to three or more lymph nodes, but not to distant sites.

Stage 4: The cancer has spread to distant lymph nodes or to other body tissue or organs.

Where Does Small Intestine Cancer Spread To?

When Stage 4 small intestine cancer spreads to distant sites, it most often invades the liver or the lining of the abdominal cavity.