Editing 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

== '''Risk factors''' (for any mass) ==

* 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

== Differential diagnosis ==

=== '''Benign lesions''' (see separate topic) ===

* 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

=== '''Malignant''' (descending order of prevalence) ===

* '''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

== '''Presentation''' ==

* '''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

== '''DDx''' ==

* Adhesions
* Hernia entrapment
* IBD
* Endometriosis
* Splenosis
* Complications from appendicitis or diverticulitis

== '''Location''' ==

* Malignant tumour proportion based on location:


== '''Diagnosis''' ==

* 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


== '''Workup''' ==
[[Category:Small bowel]]