Small Bowel Tumours
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Direct answer
Paradoxically, the small intestine — most of the gut's length and absorptive surface — hosts only a small fraction of gastrointestinal malignancies, which is exactly why its tumours stay notorious for late diagnosis. The four that matter are adenocarcinoma (duodenum and proximal jejunum, linked to Crohn's disease and coeliac disease), carcinoid tumour (ileum and appendix, serotonin-producing, second in frequency), lymphoma (ileocaecal region, non-Hodgkin type, the commonest paediatric small-bowel malignancy), and gastrointestinal stromal tumour (GIST, CD117-positive, driven by c-KIT mutations and responsive to imatinib). Presentation clusters into obscure recurrent bleeding, intermittent obstructive colic from intussusception, and perforation or mass effect; workup of obscure GI bleeding therefore always keeps a small-bowel tumour on the list until excluded by capsule endoscopy, CT enterography or enteroscopy.
What you must remember
- Benign players: adenomas, lipomas (classic cause of adult intussusception), leiomyomas, hamartomas of Peutz-Jeghers syndrome with circumoral pigmentation.
- Malignant quartet with sites: adenocarcinoma — duodenum/proximal jejunum; carcinoid — terminal ileum and appendix; lymphoma — ileocaecal area; GIST — anywhere, commonly stomach then jejunum.
- Carcinoid facts: serotonin secreted, carcinoid syndrome (flushing, diarrhoea, bronchospasm, right-sided valvular disease) appears only after hepatic metastases; urinary 5-HIAA confirms.
- GIST facts: CD117 (c-KIT) and DOG1 immunostains define it; bleeding is the usual mode; imatinib is the targeted therapy for unresectable or metastatic disease.
- Risk states: Crohn's disease (adenocarcinoma at strictures), coeliac disease (lymphoma and jejunal carcinoma), familial adenomatous polyposis (duodenal adenomas), immunosuppression.
- Diagnostic ladder for obscure bleeding: repeat endoscopy, capsule endoscopy, CT enterography, then double-balloon enteroscopy for biopsy or therapy.
- Surgical principle: segmental resection with clear margins and adjacent mesentery; carcinoid demands lymphadenectomy, and metastatic carcinoid responds to somatostatin analogues such as octreotide.
How to work through an obscure bleed
A 55-year-old man has had three hospital admissions for iron-deficiency anaemia with melaena; both upper endoscopy and colonoscopy, done well, were normal. The next move is not repeat esophagogastroduodenoscopy but capsule endoscopy, which spots a fungating jejunal lesion; CT enterography then maps a focal mass without obstruction. At laparotomy, an 8 cm proximal jejunal tumour with a bleeding ulcerated apex — histology later returns a GIST, CD117-positive, resected with clear margins; risk stratification by size and mitotic index decides adjuvant imatinib. The alternative arc matters equally: had the capsule shown a submucosal ileal mass with a mesenteric desmoplastic reaction and liver deposits, the diagnosis is ileal carcinoid — resect with lymphadenectomy, biopsy the liver lesion, and control syndrome symptoms with octreotide. Same presenting complaint, two entirely different operations and prognoses: that is why the site-and-histology matrix is worth memorising.
Where students slip
Candidates forget that adult intussusception is almost always pathological — a tumour lead point, classically a lipoma or GIST — whereas childhood intussusception is usually idiopathic ileocaecal; the exam tests exactly this inversion. The second slip is over-calling carcinoid syndrome: flushing and diarrhoea without liver metastases is rarely carcinoid, because gut serotonin is cleared by the portal circulation. Third, do not confuse GIST with leiomyosarcoma on old nomenclature — modern immunohistochemistry (CD117, DOG1) separated them, and that separation is what makes imatinib the answer to the "targeted therapy" question.
Frequently asked questions
Which are the four common small-bowel malignancies?
Adenocarcinoma, carcinoid tumour, lymphoma and gastrointestinal stromal tumour, with registry data now placing carcinoid ahead of adenocarcinoma in incidence in Western series.
When does carcinoid syndrome appear clinically?
Only when serotonin reaches the systemic circulation — typically after hepatic metastases or a primary outside portal drainage — with flushing, secretory diarrhoea, bronchospasm and right-sided valvular fibrosis.
What defines a gastrointestinal stromal tumour?
A mesenchymal tumour driven by c-KIT or PDGFRA mutations, staining positive for CD117 and DOG1, treated by resection with imatinib for advanced disease.
Which investigations find a hidden small-bowel source of bleeding?
Capsule endoscopy first, CT enterography for mural and metastatic mapping, and double-balloon enteroscopy when biopsy, tattooing or therapy is needed.
Why does adult intussusception demand surgery?
Because a tumour lead point — lipoma, GIST or carcinoma — underlies the majority of adult cases, so en bloc resection rather than pneumatic reduction is the rule.