TUMOURS OF THE SMALL INTESTINE

Question 1

What are the suggestions for why small bowel tumours are so rare?

Answer 1

fluidity and relative sterility of small bowel contents and the rapid transit time - reducing the time of exposure to potential carcinogens.
high population of lymphoid tissue and secretion of IgA in the small intestine protect against malignancy.

Question 2

Where do most small bowel tumours arise from within the small intestine?

Answer 2

55-80% in duodenum
10-25% jejunum
5-15% ileum

Question 3

What type of tumours are found within the small bowel?

Answer 3

Benign tumours - typically adenomas. Others include leiomyomas, lipomas and Desmoid tumours
Malignant tumours - adenocarcinomas, neuroendocrine tumours. Others include stromal tumours, sarcomas and lymphomas

Question 4

How are adenomas of the small intestine sub classified?

Answer 4

As simple villus, tubular or brunner’s gland adenomas

Question 5

Where are adenocarcinomas usuully found within the small intestine?

Answer 5

Duodenum - periampullary region (and also often in the jejunum)

Question 6

Where are neuroendocrine tumours usuully found within the small intestine?

Answer 6

Ileum

Question 7

Whats the most common tumour of the small intestine?

Answer 7

Adenocarcinoma - accounts for up to 50% of primary tumours

Question 8

Where are lymphomas usuully found within the small intestine? What type of lymphomas are these?

Answer 8

Ileum
Of the non-hodgkin’s type (most common in developed countries is B cell type arising from MALT)

Question 9

Outline the pathophysiology of small bowel adenocarcinomas?

Answer 9

Small intestine adenocarcinomas are believed to arise from pre-existing adenomas through a sequential accumulation of genetic abnormalities which can occur over several years.

The tumour suppressor gene p53 and the oncogene KRAS have been implicated in over 50% of small bowel adenocarcinoma cases.

Question 10

What are the risk factors of small bowel cancers?

Answer 10

Increasing age
Crohn’s disease
Coeliac disease
Certain genetic conditions e.g. lynch syndrome, FAP, Peutz-Jeghers sundrome
Smoking
Obesity
Low fibre intake
High intake of red meats
Alcohol excess

Question 11

What are the clinical features of small bowel tumours?

Answer 11

Initially asymptomatic but as they increase in size they become symptomatic by causing a small bowel obstruction due to luminal narrowing (or rarely through intussusception)
Less commonly they can present with PR bleeding
O/E - abdominal mass palpable in 25% of cases
If metastatic disease… cachexia, jaundice, hepatomgaly or ascites
Neuroendocrine tumours can also present with carcinoid syndrome

Question 12

How are small bowel tumours investigated?

Answer 12

Blood tests are non-specific - CEA levels may be raised in the presence of liver mets and 5-HIAA may be raised in carcinoid syndrome

Upper GI endoscopy for proximal duodenal small bowel tumours
MRI enterography or endoscopic ultrasound or capsule endoscopy
CT imaging

Question 13

How are adenocarcinomas managed?

Answer 13

Surgically with a segmental resection

Question 14

How is intestinal lymphomas managed?

Answer 14

With surgery and radiotherapy with chemotherapy for more extensive disease

Question 15

Where do carcinoid tumours originate from?

Answer 15

Enterochromaffin cells of intestine (these are a subset of neuroendocrine tumours)

Question 16

Where do carcinoid tumours of the intestine usually affect?

Answer 16

Appendix and terminal ileum

Question 17

What proportion of carcinoid tumours present as acute appendicitis?

Answer 17

10%

Question 18

What proportion of carcinoid tumours are associated with carcinoid syndrome?

Answer 18

10%

Question 19

What is carcinoid syndrome?

Answer 19

Often occurs when a carcinoid tumour has spread to the liver and the tumour produces an excessive amount of serotonin (i.e. liver doesnt work to break down excessive serotonin)
Symptoms include purple skin flushing predominantly on face and neck, telangiectasia, abdo pain, recurrent watery diarrhoea, cardiac abnormalities, hepatomegaly

Question 20

How is carcinoid syndrome managed?

Answer 20

Octreotide and lanretoide - somatostatin analogues that can inhibit the releas of many gut hormones

Question 21

What is Peutz-Jeghers syndrome?

Answer 21

A rare disorder where hamartomatous polyps form in the intestines so the person has a higher risk for developing certain cancers
Autosomal dominant genetic condition

Question 22

What are the 2 main types of appendiceal cancer?

Answer 22

Epithelial type and neuroendocrine type