Small bowel mass

Epidemiology

Small bowel is responsible for <2% of primary GIT malignant neoplasms
- More dilute and liquid contents of small bowel may cause less mucosal irritation than in the colon
- Rapid transit may reduce contact with carcinogens
- Lower bacterial load may reduce carcinogen exposure
- Increased lymphoid tissue may be protective
- Certain protective enzymes are only present in SB to metabolise carcinogens
High cancer rates among Maori and ethnic Hawaiians, low in Indians and Eastern Europeans
Overall slow increase in incidence in USA - mostly driven by rise in NETs
Mean age at diagnosis of 65yo for SB tumours in general

Genetic - FAP, Peutz-Jeghers, HNPCC
Chronic inflammation - coeliac, IBD, CF
Structural - Meckel's
Prior PUD
Previous cholecystectomy
May contribute:
- Dietary - processed sugar, smoked/cured meats/red meat
- Smoking
- Heavy alcohol consumption

Approach
- Mostly asymptomatic
- If symptomatic, more likely to present with GIT bleed, not abdo pain
- Consideration of excising includes malignant potential, as well as symptomatology
- Resect when found - probably will become symptomatic in the future
Adenoma
Lipoma
Leiomyoma
Hamartoma
Haemangioma
Desmoid tumour
Lymphangioma
Fibromyxoma
Ganglioneuroma

NET (neuroendocrine tumour) (44%)
- See separate topic
Adenocarcinoma (33%)
- See separate topic
Lymphoma (8%)
- See separate topic
Mesenchymal tumours (GIST) (17%)
- See 'GIST' under 'UGIS' and separate topic in this section
- Also leiomyosarcoma
Metastatic disease
- Generally the result of severe disease with overwhelmingly poor prognosis
  - Exceptions - melanoma and RCC, where significantly improved prognosis can be found after resection
- Palliative bypass can be considered
- Self-expandable metal stents can be placed in those with low performance status
- Gastrostomy/jejunostomy can be considered
- Extraluminal involvement
  - Peritoneal carcinomatosis
  - Gastric
  - Colon
  - Ovarian
- Haematogenous spread
  - Melanoma (most common - found in >50% of patients with palliative melanoma)
  - Colon
  - Breast
  - Kidney
  - Lung
  - Sarcoma

Can't reliably differentiate between benign and malignant based on clinical presentation alone
Malignant neoplasms account for 75% of symptomatic lesions that lead to surgery
Majority of symptomatic lesions are malignant
- 94% of malignant lesions were symptomatic in one series, vs 53% of benign tumours
- Malignant lesions present with abdominal pain more commonly than bleed - bleeding is more commonly related to benign tumours
Most benign lesions are asymptomatic
Often vague
- Pain (44-90%)
  - (most often related to partial obstruction),
- Nausea/vomiting (17-64%)
- Weight loss (24-44%) - mostly associated with malignant tumours
- GIT bleeding (23-41%)
Obstruction is usually secondary to intussusception
- Benign small tumours are the most common cause of this in adults
Estimated that 10% of occult GI bleeds are secondary to small bowel tumours, but life-threatening haemorrhage is uncommon

Only 50% of symptomatic patients have the correct pre-op diagnosis
Upper GIT series with small bowel follow-through
- Specificity 53-83% for malignant neoplasms
CT abdo/pelvis
- Good for GIST
- Useful for staging
CT enteroclysis
- Diagnostic accuracy of 95%
MRI enteroclysis
- Sensitivity 98%, specificity 97%
Double-balloon enteroscopy
- Reserved for cases which require a tattoo
Capsule endoscopy
- Sensitivity 89-95% and specificity 75-95% for diagnosis of a small bowel tumour in the setting of occult bleeding
FDG PET
- Useful for lesions >1cm
DOTATATE PET
- Useful for suspected NET