21. Large Bowel Tumours Flashcards
What is a polyp?
Mass arising form mucosal epithelium or submucosa, protruding into the lumen
What are the types of non-neoplastic polyps?
Hyperplastic
Hamartomatous (Juvenile and Peutz-Jehger)
Inflammatory
Lymphoid
What are hyperplastic polyps?
Glands with goblet cells and serrated appearance
Due to delayed shedding of surface epithelium
Very common in people over 60
What are juvenile polyps?
Hamartomatous malformations of bowel mucosa
Dilated glands and inflamed stroma
What are juvenile polyps known as in adults?
Retention polyps
What description is used for Peutz-Jegher polyps?
Christmas tree
What is Peutz Jegher syndrome?
AD
Mucocutaneous pigmentation
Polyps throughout GIT
Increase risk of pancreas, breast, lung, ovary and uterine cancers
What is Cowden syndrome?
AD: mutation in PTEN gene
Multiple hamartomatous polyps and skin tumours
Increased risk of thyroid and breast cancer
What is Cronkhite Canada syndrome?
Hamartomatous polyps
Nail atrophy
Skin pigmentation
What are inflammatory polyps?
Inflamed regenerative mucosa surrrounded by ulcerated tissue
Seen in IBD
What are neoplastic polyps?
Proliferation of dysplastic epithelium
Precursor to carcinoma
Can be tubular, villous (higher risk) or tubulovillous
What are the clinical features of neoplastic polyps?
Asymptomatic
Bleeding, iron deficiency anaemia
Protein loss
Obstruction
What gene is mutated in FAP?
APC gene on 5q21
What is the treatment for FAP?
Remove whole colon as 100% risk of carcinoma in 10-15 years
Name 2 variations of FAP
Gardener’s
Turcot’s
What is Gardener’s syndrome?
many benign tumours, abnormal teeth
Increased risk of duodenal and thyroid cancer
What is Turcot’s syndrome?
Colorectal adenomatous polyps
Brain tumours
What are the risk factors for colonic adenocarcinoma?
Adenomatous polyps
Hereditary syndromes (Lynch and FAP)
IBD
Diet, obesity, physical inactivity
What are the features of colonic adenocarcinoma in Lynch syndrome?
No adenoma-carcionoma sequence (straight to carcinoma)
Usually right sided
What are the differences between type 1 and 2 lynch syndrome?
1 is just increased risk of colon cancer
2 has an increased risk of colon cancer, and endometrial and ovarian
What is lynch syndrome caused by?
Defect in mismatch repair genes
What infection is associated with colonic carcinoma?
Strep bovis endocarditis
What are the macroscopic features of right sided adenocarcinoma?
‘Cauliflower’ appearance
May ulcerate and bleed: iron deficiency anaemia
What are the macroscopic features of left sided adenocarcinoma?
More likely to encircle the colon in a ‘napkin ring’ appearance
Causes constriction and obstruction as left sided lumen is narrow and faeces are more solid
Poorer prognosis
What are the histological features of adenocarcinoma of the bowel?
Produce mucin
Signet ring appearance (mucin)
CEA marker
Where is colonic carcinoma most likely to metastasise to?
Liver and Lungs
What staging system is used for colonic adenocarcinoma?
Duke’s staging
Why are NSAIDs protective against colonic adenocarcinoma?
Reduce proliferation and angiogenesis
Increase apoptosis
What are the targeted treatment options for colonic adenocarcinoma?
Cetuximab and panitumumab block EGFR signalling pathoway
Bevacizumab prevents angiogenesis
What must be done before prescribing cetuximab?
Use PCR to make sure there is no mutation in k-ras or the patient will not respond to therapy
Which organs metastasise to the colon?
Melanoma
Ovary
Endometrial
Prostate
Why does carcinoid syndrome only affect the right heart?
5-HT is broken down in the lung so never gets to the left heart
Which cells do GISTs originate in?
Interstitial cells of Cajal
What mutations are associated with GISTs?
Platelet Derived Growth Receptor a mutation
c-kit proto-oncogene
Which therapy targets the c-kit oncogene?
Imatinib
Is B or T cell lymphoma more common in the GIT?
B cell; all except EATL
