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Path - Tumours of Small + Large Intestines (iii) (Carcinoid tumours…
Path - Tumours of Small + Large Intestines (iii)
Carcinoid tumours
tumours of neuroendocrine cells
present throughout GIT
most common sites
appendix
small bowel
rectum
stomach
colon
may secrete numerous bioactive hormones (esp serotonin)
low grade malignant tumours
behaviours correlates with size, location + depth of penetration
solitary or multicentric firm yellow-tan nodules
usually submucosal masses, sometimes with ulceration
cause striking desmoplastic response (growth of fibrous or connective tissue)
form islands, trabeculae, glands, sheets
monotonous speckled nuclei + abundant pink cytoplasm
contain cytoplasmic secretory dense-core granules
asymptomatic
can cause obstruction + bleeding
may release their products into the circulation
gastrin (Zollinger Ellison syndrome)
ACTH (Cushing syndrome)
insulin (hypoglycaemia)
serotonin syndrome
seen only with massive liver mets (5HT normally degraded here)
hep mets not required for extra GI carcinoids
excess serotonin detected in blood + urine
vasomotor disturbances (skin flushing)
intestinal hypoermotility (diarrhoea/cramps)
bronchospasm (wheezing, cough)
systemic fibrosis/desmoplasia
with cardiac involvement (right ventricular subendocardial fibrosis)
right ventricular subendocardial fibrosis, pul + tricuspid valve
left heart okay as lungs inactivate 5HT
hepatomegaly (due to mets)
symptoms can be triggered by alcohol or emotional stress
Mesenchymal tumours
benign lipoma, leiomyoma, schwannoma
GISTs
Mesenchymal neoplasms of GIT
arise from pacemaker cells of GIT - myenteric interstitial cells of Cajal (create bioelectrical slow wave that leads to smooth muscle contraction)
2/3 in stomach
25% in SI
<10% CR
can be benign, borderline or malignant - depends on site, size, mitotic count
mutations in c-kit protooncogene or PDGFRA (platelet- derived growth factor receptor alpha) - increased tyrosine activity
can be blocked by gleevec (imatinib)
GI lymphoma
most common primary extra nodal lymphoma location (usually lympomases occur in nodes, , but when they don't it's usually GIT)
risk factors
H pylori infection
B cell gastric lymphoma aka MALToma aka marginal zone lymphoma
attracts inflamm cells which mutate
coeliac disease
proximal bowel
T cell lymphoma - EATL
immunodeficiency
B cell lymphoma
congenital
HIV
drugs
Mediterranean lymphoma (B cell lymphoma)