3 - pathology of colon

Question 1

what is a polyp?

Answer 1

protrusion above an epithelial surface

→it’s a tumour (swelling), can be benign, malignant, polyp of consequence etc

Question 2

what are the different shapes of polyp?

Answer 2

• pedunculated
• sessile
• flat

Question 3

what are different types of polyps?

Answer 3

can be epithelial or mesenchymal (and there are benign and malignant subtypes of each)

Question 4

what are the commonest colonic polyps?

Answer 4

1. adenomas
2. serrated polyps
3. inflammatory polyps
4. polypoid carcinoma
5. other

Question 5

what is adenoma of colon?

Answer 5

= benign tumours, not invasive and don’t metastasis but may evolve into cancers
- all adenomas are dysplastic (disordered, chaos, nucleus not neatly lined at bottom, pseudostratified)

Question 6

what are different shapes of adenoma of colon?

Answer 6

• tubullovillous
• tubular
• villous

Question 7

what is the sequence of adenoma carcinoma? what does this mean?

Answer 7

normal mucosa→adenoma (dysplastic) →adenocarcinoma (invasive)
- means ALL adenomas must be removed as all potentially premalignant, either done endoscopically or surgically

Question 8

what is colorectal carcinoma?

Answer 8

• predominantly left sided disease presenting with blood PR, altered bowel habit,obstruction
• right sided (caecum & ascending) presents means anaemia & weight loss

→because needs to be bigger to block on right and tumour obstructs faeces on left

Question 9

what is primary treatment for colorectal carcinoma?

Answer 9

surgical - colon/rectum removed

Question 10

what varies in colon carcinoma?

Answer 10

• may form polypoid or ulcerating mass
• tumour may obstruct lumen
• tumour may invade through bowel wall to involve pericolic fat
• some tumours spread to regional lymph nodes

Question 11

what does colon carcinoma look like microscopically?

Answer 11

• moderately differentiated
• dirty necrosis pattern

tumour glands invade through muscle coat

Question 12

what is TNM staging?

Answer 12

measuring severity of cancer - derived from DUKE staging

T1 or T2 = Tumour confined by muscularis propria

T3 or T4 = Tumour through muscularis propria

Any T = Tumour metastatic to lymph nodes

Question 13

how does colorectal cancer kill you?

Answer 13

• spread through local invasion to mesorectum, peritoneum and other organs
• spread through lymphatic by mesenteric nodes
• spreads haematogenous to liver and distant sites

Question 14

what are common diseases of small bowel?

Answer 14

• Diverticular disease
• Ischaemia
• Antibiotic induced colitis
• Microscopic Colitis
• Radiation colitis
• Inflammatory bowel disease and colon cancer

Question 15

what is diverticular disease?

Answer 15

• common
• often asymptomatic
• related to low fibre diet & increased intraluminal pressure
• produces outpouching of colonic mucosa that penetrate through bowel wall
• symptoms only if complicated →surgery

Question 16

what are complications of diverticular disease?

Answer 16

• inflammation
• rupture
• abscess
• fistula
• massive breathing

Question 17

what is ischaemia of large bowel?

Answer 17

• elderly
• left sided disease

more common in water shed areas e.g where SMA and IMA meet

Question 18

what are causes of ischaemia of large bowel?

Answer 18

• CVS disease
• Afib
• embolus
• shock
• vasculitis
• atherosclerosis of mesenteric vessels

Question 19

what are histological signs of ischaemia of large bowel?

Answer 19

• withering of crypts
• ‘pink smudgy lamina propria’
• ‘fewer chronic inflammatory cells’
• Clinical context:
• Elderly people
• Left sided
• Segmental on endoscopy

Question 20

what are complications of ischaemia of large bowel?

Answer 20

massive bleeding, rupture, stricture

Question 21

how can broad spectrum antibiotics cause ischaemia of bowel?

Answer 21

caused by broad spectrum antibiotics

• (c.difficile can thrive and grow), toxin A&B attack endothelium + epithelium, massive diarrhoea & bleeding →may need surgery
• histologically you can see explosive volcano like eruptions of purulent exudate

Question 22

what is collagenous collitis?

Answer 22

= form of microscopic colitis

• normal chronic mucosa
• thickened basement membrane
• Normal is between 2-3 microns
• Disease is patchy
• Associated with intraepithelial inflammatory cells
• No chronic architectural changes
• Check clinical history for watery diarrhoea, normal endoscopy, drug history etc

Question 23

what is lymphocytic collitis?

Answer 23

= another type of microscopic colitis

• No chronic architectural changes in crypts
• Intraepithelial lymphocytes are raised
• No thickening of BM
• Check for correct history, normal endoscopy
• Raise possibility of Coeliac disease in report

Question 24

what is microscopic colitis?

Answer 24

• A misnomer somewhat
• Normal endoscopy
• Useful for cases with mixed features of CC and LC
• Should use in appropriate clinical context
• Not Crohn’s or UC
• Be prepared to reclassify on subsequent biopsies

Question 25

what is diverticulitis?

Answer 25

= colon gets outpouching and poo collects in outpouch and can get inflamed or infected (very bad infection if poo pops out)