Small Bowel Tumor
A small bowel tumor is a growth arising from the wall of the duodenum, jejunum, or ileum. Small bowel tumors are much less common than tumors of the stomach or colon, despite the small bowel being much longer than the large bowel. They include a wide range of conditions: benign tumors such as lipomas, leiomyomas, and hamartomas; malignant tumors such as adenocarcinoma, neuroendocrine tumors (carcinoids), lymphoma, gastrointestinal stromal tumors (GISTs); and metastases from other cancers. The small bowel’s length and location make evaluation challenging, and small bowel tumors are frequently diagnosed later than tumors elsewhere. Specialized imaging (CT enterography, MR enterography) and endoscopic techniques (capsule endoscopy, deep enteroscopy) are essential for diagnosis. Treatment depends entirely on the specific tumor type.
What is it?
The small bowel (small intestine) is the longest part of the gastrointestinal tract, extending from the stomach to the large intestine over about 6 to 7 meters in adults when measured at surgery (somewhat longer in autopsy studies where the muscle is relaxed). It is divided into three sections: the duodenum (the shortest and first portion, receiving material from the stomach along with bile and pancreatic secretions; the site of much digestion and absorption of iron and calcium); the jejunum (the middle portion, where most nutrient absorption occurs); and the ileum (the last portion, which absorbs specific nutrients including vitamin B12 and bile acids, and which contains substantial lymphoid tissue including Peyer’s patches).
Despite this substantial length, tumors of the small bowel are much less common than tumors of the stomach or colon. Small bowel cancers account for a small proportion (typically cited as around 3–5%) of all gastrointestinal cancers. Reasons for the relative rarity are not entirely clear but likely include the rapid transit of contents through the small bowel (reducing time for potential carcinogens to interact with the mucosa), the alkaline environment, lower bacterial load, high concentration of immune cells including IgA, high cell turnover with rapid clearance of damaged cells, and other factors.
Small bowel tumors include a wide range of both benign and malignant conditions.
Benign small bowel tumors include:
– Adenomas — precancerous glandular polyps, similar to those in the colon; particularly common in the duodenum and can be associated with familial adenomatous polyposis (FAP)
– Lipomas — benign tumors of fat tissue
– Leiomyomas — benign smooth muscle tumors
– Hamartomas — mixed tissue growths, characteristic of Peutz-Jeghers syndrome (which also causes distinctive dark spots on the lips and mouth)
– Brunner gland tumors — benign duodenal tumors
– Neurogenic tumors (such as schwannomas)
– Others
Malignant small bowel tumors include:
– Adenocarcinoma — the most common small bowel cancer overall, with the duodenum being the most common site (particularly the periampullary region near where the bile and pancreatic ducts enter the duodenum), followed by the jejunum and ileum
– Neuroendocrine tumors (carcinoids) — the second most common small bowel cancer overall, with the ileum being the most common site; often small and multifocal (see also our Bowel Carcinoid page)
– Lymphoma — most commonly diffuse large B-cell lymphoma, but including other subtypes; the ileum is a common site; can be primary or secondary to widespread lymphoma
– Gastrointestinal stromal tumors (GISTs) — tumors arising from the interstitial cells of Cajal in the bowel wall; can occur throughout the small bowel and are the most common non-epithelial tumor
– Metastases from other cancers — including from lung, breast, melanoma, ovary, and other primary cancers; melanoma has a particular tendency to metastasize to the small bowel
Several conditions increase the risk of small bowel tumors:
– Crohn’s disease—significantly increases the risk of small bowel adenocarcinoma, particularly with long-standing disease
– Celiac disease—increases the risk of small bowel adenocarcinoma and, in specific cases, enteropathy-associated T-cell lymphoma
– Lynch syndrome (hereditary nonpolyposis colorectal cancer)—increases the risk of small bowel adenocarcinoma
– Familial adenomatous polyposis (FAP)—causes multiple duodenal adenomas and increases the risk of duodenal adenocarcinoma (which is now one of the leading causes of death in FAP patients whose colon has been removed)
– Peutz-Jeghers syndrome—characterized by hamartomatous polyps throughout the gastrointestinal tract (particularly the small bowel) and characteristic dark spots on the lips and mouth; increases the risk of small bowel and other cancers
– Neurofibromatosis type 1—associated with an increased risk of specific small bowel tumors including neuroendocrine tumors and GISTs
– MEN1 syndrome—associated with duodenal neuroendocrine tumors (particularly gastrinomas in Zollinger-Ellison syndrome)
Symptoms of small bowel tumors are often nonspecific and vague, contributing to what is often a significant delay between symptom onset and diagnosis. Common symptoms include abdominal pain (often intermittent and crampy), unexplained weight loss, nausea and vomiting (particularly with obstruction), gastrointestinal bleeding (which may be occult and cause iron-deficiency anemia over time, or, less commonly, visible blood or black tarry stools), symptoms of small bowel obstruction (colicky abdominal pain, distention, vomiting, inability to pass stool or gas), a palpable abdominal mass in some cases, and, with duodenal tumors near the ampulla, jaundice.
Small bowel tumors can also present with complications such as intussusception (telescoping of one segment of bowel into another, in which a tumor serves as the leading edge), bowel obstruction, perforation, or significant bleeding.
Some small bowel tumors are identified incidentally on imaging performed for other reasons, particularly small tumors or those with characteristic features.
Diagnosis of small bowel tumors is often challenging because the mid and distal small bowel are difficult to reach with standard endoscopy and can be difficult to evaluate with standard imaging. Multiple modalities are often needed:
Standard CT of the abdomen and pelvis with intravenous and oral contrast is often the initial imaging test and may identify larger tumors and complications such as obstruction. However, standard CT has limitations for detailed small bowel evaluation.
CT enterography and MR enterography are dedicated protocols designed for small bowel evaluation. Both involve consumption of a large volume of low-attenuation oral contrast to distend the small bowel and provide detailed views of the bowel wall. CT enterography provides high-resolution images relatively quickly but involves radiation. MR enterography avoids radiation and provides excellent soft tissue contrast, and is particularly useful for younger patients, patients with Crohn’s disease requiring repeated imaging, and for detailed evaluation of specific findings.
Capsule endoscopy (in which the patient swallows a small camera that images the bowel as it passes through) is highly sensitive for identifying mucosal lesions in the small bowel, particularly those that may cause obscure gastrointestinal bleeding. It cannot obtain biopsies or provide detailed staging, and is generally not appropriate when significant obstruction is suspected because the capsule could become stuck.
Deep enteroscopy (with balloon-assisted or spiral techniques) is an advanced endoscopic technique that allows the endoscope to reach farther into the small bowel than standard enteroscopy. It can be performed from above (antegrade, through the mouth) or below (retrograde, through the colon), and often can reach much of the small bowel with both approaches. Deep enteroscopy allows biopsy and, in some cases, therapeutic interventions such as polyp removal or bleeding control.
Standard upper endoscopy evaluates the stomach and proximal duodenum and can identify and biopsy tumors in these locations.
Standard colonoscopy can sometimes reach the terminal ileum, providing evaluation and biopsy of tumors in this specific area.
PET/CT is useful for staging in specific circumstances, particularly for suspected small bowel adenocarcinoma or lymphoma. Ga-68 DOTATATE PET/CT is a specialized nuclear medicine study that is particularly sensitive for identifying neuroendocrine tumors.
Blood tests including complete blood count (which may show iron-deficiency anemia from occult bleeding), kidney and liver function, and, when appropriate, tumor markers or hormonal studies (such as chromogranin A and 5-HIAA for suspected neuroendocrine tumors) are typically performed.
Biopsy provides definitive diagnosis and can be obtained through endoscopic techniques when the tumor is accessible or through image-guided or surgical approaches otherwise.
For patients with suspected hereditary syndromes, genetic counseling and, when appropriate, genetic testing are important.
Important to Know
Management of small bowel tumors depends entirely on the specific tumor type, stage, location, and patient factors. Care is best delivered by multidisciplinary teams that include general surgeons or surgical oncologists (particularly those with small bowel expertise), medical oncologists, gastroenterologists with small bowel expertise, radiologists, pathologists, geneticists (when relevant), and, when needed, other specialists.
For benign small bowel tumors, management depends on the specific tumor type, location, size, and symptoms. Small asymptomatic benign tumors identified incidentally may be observed or, when accessible endoscopically, removed. Larger tumors, symptomatic tumors, or those with concerning features may require surgical resection.
For small bowel adenocarcinoma, treatment principles broadly follow those for colon cancer, though outcomes have historically been poorer, in part because of delayed diagnosis. Surgery is the mainstay of curative treatment and typically involves segmental resection of the affected small bowel with removal of associated mesentery containing lymph nodes. Duodenal adenocarcinoma near the ampulla may require a Whipple procedure (pancreaticoduodenectomy)—a complex operation involving removal of the duodenum, part of the pancreas, and other structures. Adjuvant chemotherapy after surgery is often considered for higher-stage disease. For metastatic small bowel adenocarcinoma, systemic chemotherapy (with regimens similar to those used for metastatic colon cancer) and, in appropriate patients, targeted therapies based on molecular characteristics are used.
For neuroendocrine tumors of the small bowel (which are often multifocal), surgical resection includes careful examination of the entire small bowel to identify and remove all tumors, along with wide resection of the mesentery containing lymph nodes. For advanced disease, treatments include somatostatin analogues (octreotide and lanreotide), peptide receptor radionuclide therapy (PRRT) with lutetium-177 DOTATATE, targeted therapies (such as everolimus), and liver-directed therapies for liver metastases (see also our Bowel Carcinoid page).
For gastrointestinal stromal tumors (GISTs) of the small bowel, treatment includes surgical resection for localized disease—typically involving segmental resection with negative margins, without the need for wide lymph node dissection (as GISTs rarely spread to lymph nodes). Targeted therapy with imatinib (and, in specific circumstances, other tyrosine kinase inhibitors such as sunitinib or regorafenib) has transformed the treatment of GIST. Imatinib is used as adjuvant therapy after surgery for higher-risk tumors and as primary treatment for unresectable or metastatic disease. Molecular testing to identify the specific mutations (particularly KIT and PDGFRA mutations) is essential and guides treatment.
For lymphoma involving the small bowel, treatment follows lymphoma-specific principles based on the specific subtype and typically involves chemoimmunotherapy (such as R-CHOP for DLBCL) rather than primary surgical treatment. Surgery is generally reserved for complications such as perforation, obstruction, or significant bleeding (see also our Bowel Lymphoma page).
For metastases to the small bowel from cancers elsewhere, treatment focuses on the primary cancer, with local treatment of the small bowel metastasis considered in selected circumstances (particularly when causing symptoms).
For patients with hereditary syndromes:
– FAP patients require surveillance of the duodenum with regular upper endoscopy because duodenal adenomas and adenocarcinoma have become a leading cause of cancer-related death in FAP. Endoscopic removal of polyps and, in some cases, prophylactic pancreas-preserving duodenectomy or Whipple procedure may be considered for advanced duodenal polyposis.
– Peutz-Jeghers syndrome requires surveillance of the entire gastrointestinal tract with regular capsule endoscopy or MR enterography, along with removal of larger polyps to reduce the risk of intussusception or malignancy. Family screening is important.
– Lynch syndrome patients require surveillance for multiple cancer types, including consideration of periodic small bowel surveillance in some protocols.
For patients presenting acutely with complications such as bowel obstruction, perforation, or significant bleeding, urgent management is needed. Emergency surgery may be required, and the underlying diagnosis is often clarified after acute stabilization.
Nutritional considerations are important for many patients with small bowel tumors, particularly those with significant weight loss, malabsorption, or after significant small bowel resection. Extensive small bowel resection can lead to short bowel syndrome, with malabsorption and the need for nutritional support (including specialized diets or, in severe cases, parenteral nutrition). Consultation with nutrition specialists is important.
Long-term follow-up depends on the specific tumor type and includes imaging, clinical assessment, and, when appropriate, laboratory tests and endoscopy.
For patients considering fertility preservation before treatment, coordination with reproductive medicine is important.
Mental health support and support for family and caregivers are important components of care, particularly given the often chronic nature of some small bowel tumor treatments and the impact on daily life.
For patients with advanced disease, palliative care can be integrated alongside cancer-directed therapy at any stage.
Care is best coordinated by multidisciplinary teams at centers with experience in small bowel tumors, which are less common than colon or stomach tumors and benefit from specialized expertise. Clinical trials may be particularly valuable for some patients given the relative rarity of these conditions and the ongoing need for improved treatments.
Imaging, laboratory, pathology, and molecular findings are interpreted alongside the patient’s symptoms, examination, family history, and broader clinical context rather than in isolation.
Patient education plays an essential role. Understanding the diagnosis, the specific tumor type and its behavior, the rationale for the recommended treatment plan, the meaning of imaging and endoscopic findings, treatment side effects, the importance of any recommended surveillance, and warning signs of complications all contribute to better outcomes.
Red flag symptoms include severe abdominal pain, symptoms of bowel obstruction (severe abdominal pain, distention, vomiting, inability to pass stool or gas), significant gastrointestinal bleeding (large amounts of visible blood, black tarry stools, or lightheadedness with bleeding), high fever with signs of severe infection, sudden severe pain (which may suggest perforation), signs of sepsis, jaundice, unintended significant weight loss with dehydration, symptoms suggestive of intussusception (colicky abdominal pain, currant jelly-like stools, palpable mass), new severe back pain with weakness, numbness, or bowel or bladder changes, or rapid clinical deterioration. These warrant prompt or urgent medical evaluation.