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Introduction
Malignancy of the small intestine is a rare form of cancer that is diagnosed in around 1,900 people in the United Kingdom (UK) every year.1 It accounts for less than 5% of all gastrointestinal (GI) cancers, despite the small intestine making up over 90% of the mucosal surface area and 75% of the length of the digestive tract.2
Aetiology
The majority of small bowel tumours arise in the duodenum (55-82%) and less frequently can occur in the jejunum (11-25%) and ileum (7-17%).2 Around 64% of small bowel tumours are malignant, and benign tumours include adenomas, fibromas, lipomas and leiomyomas.3
Subtypes
Several types of malignant tumours may form:2-3, 5
Adenocarcinoma
Adenocarcinomas are the most common type of malignant tumour, accounting for 40% of all small bowel cancers. They arise from the glandular epithelial cells lining the small intestine and are most commonly located within the duodenum. The average age at diagnosis is 66 years old.
Neuroendocrine tumours
Neuroendocrine cells are any cells that receive input from neurotransmitters to release hormones into the bloodstream. Neuroendocrine tumours most commonly affect the ileum.
Primary malignant lymphoma
This often arises due to untreated coeliac disease in the form of enteropathy-associated T-cell lymphoma (EATL) and typically results in a long, rigid section of the small intestine.
Kaposi sarcoma
Kaposi sarcoma develops secondary to infection with human herpesvirus 8 (HHV-8) in immunocompromised patients (e.g. acquired immunodeficiency syndrome (AIDS), transplant patients). This can occur anywhere in the GI tract but typically form in the stomach or small intestine.
Pathophysiology
The pathogenesis of small bowel adenocarcinoma is thought to be similar to that of colorectal cancer. Pre-existing adenomas (developed sporadically or due to familial adenomatous polyposis) become dysplastic through the stepwise accumulation of genetic abnormalities before progressing to carcinomas-in-situ and eventually invasive adenocarcinomas over several years.5
Mutations of the p53 tumour suppressor gene and the presence of the KRAS oncogene have been implicated in over 50% of small bowel adenocarcinoma cases.2
These cancer cells may then metastasise through the lymphatic system or portal circulation to the brain, liver, lungs and bones.5
Risk factors
Non-modifiable
Non-modifiable risk factors include:7-8
- Male
- Increasing age
- African ethnicity
- Coeliac disease: autoimmune damage increases the risk of enteropathy-associated T-cell lymphoma (EATL) and small bowel cancer
- Colorectal cancer: possibly due to shared risk factors
- Crohn’s disease
- Inherited syndromes: e.g. familial adenomatous polyposis, Lynch syndrome
Modifiable
Modifiable risk factors include:7
- Smoking
- Alcohol excess
- Obesity
- Low fibre intake
- Diet high in red meats
Inherited syndromes
Familial adenomatous polyposis
Familial adenomatous polyposis (FAP) is an autosomal dominant disease that results in hundreds or thousands of adenomatous polyps forming throughout the colon and rectum, often from as early as 10 years old.9-10 If a prophylactic total colectomy is not completed, most patients develop colorectal cancer by 40 years old.3
FAP has extra-colonic manifestations that increase the risk of several other cancers, including duodenal cancer, which develops in around 12% of FAP patients from adenomas in the duodenum.10-11
Lynch syndrome (hereditary non-polyposis colorectal cancer)
This is an autosomal dominant condition present in around 1 in 400 people in the UK.13 It has an 80% lifetime risk of colorectal cancer that typically forms from a single colonic adenoma caused by defective DNA mismatch repair genes.14
Patients also have around a 60% lifetime risk of endometrial cancer as well as an increased risk of gastric, ovarian, urothelial, prostate, biliary tract and pancreatic cancers, depending on the variant.15
Clinical features
History
The asymptomatic nature of small bowel malignancies means that these tumours can be very hard to detect and diagnose in their early stages, with the time between first presentation and diagnosis averaging between six and nine months.16
Early symptoms often resemble those of colorectal cancer:8, 16-17
- Non-specific abdominal pain
- Unintentional weight loss
- Microscopic rectal bleeding: occurs in around one-third of cases of small bowel adenocarcinoma
- Melaena or fresh red rectal bleeding
- Symptoms of anaemia: fatigue, shortness of breath, chest pain, brittle nails, palpitations
Small bowel malignancies are usually first identified once the tumour has narrowed the intestinal lumen. More proximal tumours in the duodenum may block the pylorus, causing gastric outlet obstruction and preventing food contents from exiting the stomach, while more distal tumours may result in small bowel obstruction.8, 18
Clinical examination
Clinical examination is typically unremarkable in early malignancy.
An abdominal mass may be felt in around 25% of cases. There may also be evidence of glossitis, pallor and angular stomatitis in patients with iron deficiency anaemia secondary to chronic occult GI bleeding.20
Jaundice, ascites, hepatomegaly and cachexia may occur with metastatic spread and are poor prognostic factors.8 Examination often does not suggest the diagnosis until small bowel or gastric outlet obstruction occurs.
Succussion splash test
The succession splash test can suggest gastric outlet obstruction secondary to pyloric stenosis, gastric carcinoma or small bowel malignancy; it may also be present in hydropneumothorax or a large hiatal hernia.21
Gently shake the abdomen by holding either side of the pelvis while listening with the naked ear or a stethoscope. A splashing sound heard three or more hours after drinking a liquid is positive. This represents the retention of stomach contents as the liquid splashes against the walls of a full stomach.18
Table 1. Clinical features of small bowel obstruction and gastric outlet obstruction, which may be secondary to small bowel malignancy.17-18, 22
| Small bowel obstruction | Gastric outlet obstruction | |
| History |
|
|
| Exam |
|
|
Differential diagnoses
There are a significant number of differential diagnoses that may produce similar GI symptoms to small bowel malignancy including:
- Colorectal cancer
- Gastric cancer
- Coeliac disease
- Peptic ulcer disease
- Inflammatory bowel syndrome
- Inflammatory bowel disease
- Endometriosis
- Gastroparesis
- Intestinal ischaemia
- Small bowel obstruction secondary to other causes such as adhesions, hernias or volvulus
Investigations
Malignancies of the small intestine are difficult to diagnose as patients are typically asymptomatic or present with non-specific symptoms until obstruction occurs.2
Bedside investigations
Relevant bedside investigations may include:
- Weight/BMI: to quantify and monitor weight loss
Laboratory investigations
Although there are no specific tumour markers to detect small intestine malignancies, laboratory results may support the diagnosis:23
- Full blood count: microcytic anaemia secondary to iron deficiency
- Iron studies: iron deficiency from chronic GI bleeding
- Urea and electrolytes: baseline before investigations or treatment
- Liver function tests: elevated transaminases in metastases
- C-reactive protein: raised in inflammation (non-specific)
- Stool faecal immunochemical testing (FIT): to detect microscopic blood in faeces
- Tissue transglutaminase (anti-TTG) with total IgA level: to investigate for coeliac disease
- Genetic testing: for hereditary conditions such as FAP and HNPCC
- Carcinoembryonic antigen levels (CEA): may be elevated with adenocarcinomas and hepatic metastases
Imaging
Typical imaging includes:2
- CT abdomen: if features of acute intraabdominal pathology
- PET-CT imaging: staging CT to identify metastatic spread
- Upper GI endoscopy and biopsy: to identify and sample tumours in the proximal duodenum
Upper GI endoscopy often cannot identify more distal tumours, and MRI enterography, capsule endoscopy or endoscopic ultrasound may also be needed to visualise the rest of the GI tract, followed by surgical biopsy to sample a mass.2, 24
Management
Treatment options depend on the size, subtype, and location of the tumour, as well as patient factors such as age, preference, frailty, and the presence of other co-morbidities.
Conservative
Watchful waiting may be an option where tumour growth is slow or when the risks of treatment outweigh the benefits.25
This approach may also include conservative management of the complications that arise from the tumour, such as nasogastric decompression of small bowel obstruction, as opposed to surgical management of these complications.22
Medical
Typical medical management may include:25-26
- Chemotherapy (e.g. 5-fluorouracil (5-FU), capecitabine and oxaliplatin)
- Immunotherapy (e.g. pembrolizumab)
- Radiotherapy: for symptomatic relief of obstructive symptoms or metastatic brain/bone disease in palliative treatment
Surgical
Localised small bowel tumours may be definitively treated with wide segmental surgical resection, with the addition of neoadjuvant chemotherapy or chemoradiotherapy if the malignancy is locally advanced with local lymphatic spread.27
Most tumours can be removed by segmental resection. Tumours invading the ampulla or pancreas or involving the second portion of the duodenum may require a pancreatoduodenectomy (Whipple’s procedure) or segmental duodenal resection.26-27
Metastatectomy of liver metastases and surgical debulking of peritoneal metastases may be attempted in distant metastatic spread but requires significant multi-disciplinary discussion with adjuvant or neo-adjuvant systemic treatment often needed.8
Pancreatoduodenectomy (Whipple’s procedure)
This involves the removal of the head of the pancreas, duodenum, common bile duct, gallbladder, antrum of the stomach and surrounding lymph nodes before the tail of the pancreas and hepatic duct are anastomosed to the jejunum. These organs are removed as they all receive blood supply from the gastroduodenal artery.28
Although this procedure is typically completed to treat pancreatic cancer, it may also be used to treat small bowel tumours in the duodenum, pancreatic cysts, chronic pancreatitis and trauma to the pancreas or duodenum.28
Complications
The overall prognosis of small bowel malignancy remains favourable. At the time of diagnosis, 70% of patients with small bowel adenocarcinoma have potentially resectable disease.2 Small intestinal cancer accounts for less than 1% of all cancer deaths within the UK annually, and around 53% of people diagnosed with small bowel cancer in England survive for 5 years or more.1
Other complications of small bowel malignancy include those discussed above:
- Partial or complete small bowel obstruction that may result in peritonism and perforation
- Gastric outlet obstruction
- Iron deficiency anaemia
- Metastasis to other solid organs and the peritoneum22
- Death
There are also significant social, financial and psychological complications. A cancer diagnosis can cause significant emotional distress, including fear, anxiety, guilt, grief, anger and depression, and can cause a strain on relationships, leading to social isolation. Cancer symptoms and the diagnosis itself can affect a person’s self-identity, and patients often require significant amounts of time off of work and hobbies to attend medical appointments, which can cause significant financial strain secondary to medical costs, loss of income, and the need for ongoing care.30
Reviewer
Miss Kate Carney
Consultant Colorectal Surgeon
Editor
Dr Jamie Scriven
References
- Cancer Research UK. Small intestine cancer statistics. 2016. Available from: [LINK].
- Aparicio T, Zaanan A, Svrcek M, et al. Small bowel adenocarcinoma: Epidemiology, risk factors, diagnosis and treatment. Digestive and Liver Disease. 2013. Available from [LINK].
- Villano A. Small-Bowel Tumors. MSD Manual Professional Edition. 2023. Available from: [LINK].
- Blausen. Diagram showing the basic sections of the small intestine. Licence: [CC BY 3.0].
- Somasundar PS. Malignant Neoplasms of the Small Intestine. Medscape. 2022. Available from: [LINK].
- Silverman S. Intraoral Kaposi’s sarcoma lesion with overlying candida infection, inside the mouth of a patient with acquired immunodeficiency syndrome. Licence: [Public domain].
- American Cancer Society. Risk Factors for Small Intestine Cancer (Adenocarcinoma). 2018. Available from: [LINK].
- Benson AB, Venook AP, Al-Hawary MM, et al. Small Bowel Adenocarcinoma. Journal of the National Comprehensive Cancer Network. 2019. Available from [LINK].
- American Cancer Society. Colorectal Cancer Risk Factors. 2024. Available from: [LINK].
- Villano A. Familial Adenomatous Polyposis. MSD Manual Professional Edition. 2023. Available from: [LINK].
- National Cancer Institute. Drug Combo Shrinks Duodenal Polyps in FAP. 2016. Available from: [LINK].
- Calicut Medical College. Cut open section of colectomy specimen showing hundreds of small polyps throughout the entire colon. Licence: [CC BY-SA 4.0].
- NHS England. Thousands with cancer-causing condition offered life-saving NHS bowel cancer screening. 2024. Available from: [LINK].
- Villano A. Lynch Syndrome. MSD Manual Professional Edition. 2023. Available from: [LINK].
- Bhattacharya P, Leslie SW, McHugh TW. Lynch Syndrome. StatPearls. 2024. Available from: [LINK].
- Huang J, Alrawi S. Small Bowel Cancer. Medscape. 2023. Available from: [LINK].
- Ocasio Quinones GA, Khan Suheb MZ, Woolf A. Small Bowel Cancer. StatPearls. 2023. Available from: [LINK].
- Koop AH, Palmer WC, Stancampiano FF. Gastric outlet obstruction: A red flag, potentially manageable. Cleveland Clinic Journal of Medicine. 2019. Available from: [LINK].
- Wu X, Cheung HYS, Chung CCC, et al. Gross pathology of small intestinal adenocarcinoma. Licence: [CC BY 4.0].
- BMJ Best Practice. Iron deficiency anaemia – Symptoms, diagnosis and treatment. 2022. Available from: [LINK].
- GPnotebook. Succussion splash. 2018. Available from: [LINK].
- Tidy C. Intestinal Obstruction and Ileus. Patient.info. 2014. Available from: [LINK].
- Somasundar PS. Malignant Neoplasms of the Small Intestine Workup. 2022. Available from: [LINK].
- American Cancer Society. Tests for Small Intestine Cancer (Adenocarcinoma). 2018. Available from: [LINK].
- Somasundar PS. Malignant Neoplasms of the Small Intestine Treatment & Management. Medscape. 2022. Available from: [LINK].
- American Cancer Society. Treatment Choices for Small Intestine Cancer (Adenocarcinoma), Based on Tumor Spread. 2018. Available from: [LINK].
- Cusick J, Overman M, Kunitake H. Treatment of small bowel neoplasms. UpToDate. 2024. Available from: [LINK].
- D’Cruz JR, Misra S, Shamsudeen S. Pancreaticoduodenectomy (Whipple Procedure). StatPearls Publishing. 2021. Available from: [LINK].
- Cancer Research UK. Diagram showing the parts of different organs removed during a Whipple’s procedure. Licence: [CC BY-SA 4.0].
- OHSU Knight Cancer Institute. Social and Emotional Side Effects of Cancer. 2019. Available from: [LINK].
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