Colon Cancer Flashcards
what are the two main genetic pathways in colonic cancer
APC and the Mismatch repair gene pathway
describe the APC gene pathway
this is an autosomal dominant disorder which sees patients develop heaps of polyps by teenager. this is due to the mutation in the APC gene. with eh numerous polyps there is high chance of cancer development
describe the mismatch repair gene pathway
Caused by inherited mutations in mismatch repair genes that encode proteins responsible for the detection, excision, and repair of errors that occur in DNA replication. Also known as lynch syndrome. Majority mutations in MSH2 or MLH1. these genes were studied in people with lynch syndrome or Hereditary Non-Polyposis Colorectal Cancer
describe the adenocarcinoma sequence of colonic carcinogenesis
APC is a tumor suppressor gene having a mutated copy of both these genes creates driver mutations. then the person has subsequent mutations in oncogene KRAS and tumour suppressor p53. thus resulting in cancer formations
what are adenomatous polyps
benign neoplasms of the colonic mucosa that present as polyploid masses projecting from the mucosal surface; hence called polyps or adenomatous polyps
difference between the pendunculated and the sessile polyps
pendunculated have a submucosal stalk, whereas the sessile polyps have adhered to the surface of the mucosa
polyps are what
benign adenomatous glands
what are the possible architectures of the adenoma polyp
tubular - tend to be pedunculated and are composed of rounded tubular glands
villous - having villous architecture, often sessile gland type
tubulovillous - a mix of the both
the size of the polyp correlates most with what
the malignant risk of the adenoma
when are the malignant transformations of the adenomas defined
when the glands of the adenoma are seen infiltrating past the muscularis mucosae and into the submucosa
what are the gross morphological patterns of the colon cancers
the exophytic fungating and the ulcerative are the common gross morphologies of a right sided colon cancer
the diffuse infiltrating napkin ring is more common of the left sided colon cancer
clinical presentation of a right sided colon cancer
fatigue and weakness due to iron deficiency anaemia, has hidden or occult blood in the stools. not fresh blood as its so far up the GIT so it becomes the hidden occult blood
clincal presentation of a left sided colon cancer
can present with changes in bowel habits, changes in stool calibre, intestinal obstruction or cramping and left lower quadrant discomfort, and occult or fresh blood in stools
this happens because of the tendency for the left sided colon cancer to grow in a diffusely infiltrative pattern
