GI cancer SD Flashcards
(49 cards)
how long is the colon?
aprox 1.5m
what are the 4 regions of the colon?
– Ascending
– Transverse
– Descending
– Sigmoid
what is ascending colon linked to small intestine by?
the caecum
what joins the rectum?
Sigmoid colon
what are the functions of the colon?
- Reabsorption of fluids and some solutes
– 2L of water enter the colon from the ileum
– 90% reabsorbed (mainly in ascending colon)
– Fat-soluble vitamins, e.g. vitamin K, vitamin B12, thiamine, riboflavin
– Negligible; no significant impact on nutrition - Movement of waste products for excretion
– Movement by haustral contractions
– Contraction of smooth muscle
how long does it take for waste to pass?
16 hours
what are the 4 parts that make up the histology of the colon?
1- mucosa- lamina propria, crypts, muscularis mucosae
2-submucosa
3-muscularis propria
4-serosa
what is the purpose of the 3 parts of the mucosa?
- Crypts
– Columnar colonocytes
– Goblet cells (mucus-secreting)
– Stem cells - Lamina propria
– Connective tissue that provides
support & immune defence
– Lymphocytes, lymph nodules - Muscularis mucosae
– 2 layers of smooth muscle
what is the submucosa?
– Connective tissue rich in blood and
lymph vessels
what is the purpose of the muscularis propria?
– Smooth muscle in three layers
(collectively the ‘taenia coli’)
– Contraction moves faeces through the
colon
what is the purpose of the serosa?
– Thin layer of mesothelial cells
– Positioning of the colon
what is FAP?
- Inherited mutation in the APCgene
– Formation of many polyps
how do you diagnose FAP?
Diagnosed by colonoscopy and genetic
testing
– Identification of 100+ polyps
– Sequencing of the APCgene
what are the risk factors for CRC?
- Diet
– ↑red meat, processed meats
– ↓fibre, chicken & fish - Lack of physical activity
- Obesity
- Alcohol & smoking
- Genetic predisposition
- Protective effect of aspirin
where is sporadic CRC most common?
most common in the descending colon, sigmoid colon and rectum
do tumours differ by region?
- Tumours differ by region
– Ascending/transverse vs descending/
rectal
– mutations in KRAS (sigmoid/rectum)
– BRAF (ascending/transverse)
– mutually exclusive
what is the estimate time it takes for ademona to develop into an advanced carcinoma?
17 years
how long does it take for carcinoma to progress to metastasis ?
– 1.8 years from advanced
carcinoma to metastasis
what is the histology of CRC?
- Loss of normal architecture
- Hyperchromatic (intensely stained) cells
- Invasion through submucosa
- Nucleus takes up a greater proportion of the cell
what is the staging of colorectal cancer?
TNM
- tumour T1- invades submucosa
2-invades muscularis propria
3- through muscularis to pericolorectal tissues
4-penetrates to surface of visceral peritoneum/ invades or adherent to other organs
how do we stage CRC in the UK?
duke stages A-D
how does CRC metastases to the liver?
Liver is the most commonly affected site
– Venous drainage from the colon to the liver
– Liver mets affect 50% of CRC patients
– 20% will be resectable much better
prognosis (poor without)
how do lungs metastases?
- Lungs second-most commonly affected
– 10-15% of CRC patients will develop lung mets
– Rare to have lung mets alone (<10%)
– Usually not resectable
what is the vogelstein model?
Bert Vogelstein described a molecular model by which CRC could
arise, now referred to as the ‘Vogelstein model’
– Step-wise accumulation of mutations/epigenetic changes and how
they relate to tumour development
1. APCTSG, regulates Wnt signalling Mutated in ~50%
of CRC
2. KRASOncogene, drives cell growth Mutated in ~45%
3. p53TSG, ‘guardian of the genome’ Mutated in ~40%
