3 - pathology of colon Flashcards
what is a polyp?
protrusion above an epithelial surface
→it’s a tumour (swelling), can be benign, malignant, polyp of consequence etc
what are the different shapes of polyp?
- pedunculated
- sessile
- flat
what are different types of polyps?
can be epithelial or mesenchymal (and there are benign and malignant subtypes of each)
what are the commonest colonic polyps?
- adenomas
- serrated polyps
- inflammatory polyps
- polypoid carcinoma
- other
what is adenoma of colon?
= 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)
what are different shapes of adenoma of colon?
- tubullovillous
- tubular
- villous
what is the sequence of adenoma carcinoma? what does this mean?
normal mucosa→adenoma (dysplastic) →adenocarcinoma (invasive)
- means ALL adenomas must be removed as all potentially premalignant, either done endoscopically or surgically
what is colorectal carcinoma?
- 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
what is primary treatment for colorectal carcinoma?
surgical - colon/rectum removed
what varies in colon carcinoma?
- 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
what does colon carcinoma look like microscopically?
- moderately differentiated
- dirty necrosis pattern
tumour glands invade through muscle coat
what is TNM staging?
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
how does colorectal cancer kill you?
- spread through local invasion to mesorectum, peritoneum and other organs
- spread through lymphatic by mesenteric nodes
- spreads haematogenous to liver and distant sites
what are common diseases of small bowel?
- Diverticular disease
- Ischaemia
- Antibiotic induced colitis
- Microscopic Colitis
- Radiation colitis
- Inflammatory bowel disease and colon cancer
what is diverticular disease?
- 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
what are complications of diverticular disease?
- inflammation
- rupture
- abscess
- fistula
- massive breathing
what is ischaemia of large bowel?
- elderly
- left sided disease
more common in water shed areas e.g where SMA and IMA meet
what are causes of ischaemia of large bowel?
- CVS disease
- Afib
- embolus
- shock
- vasculitis
- atherosclerosis of mesenteric vessels
what are histological signs of ischaemia of large bowel?
- withering of crypts
- ‘pink smudgy lamina propria’
- ‘fewer chronic inflammatory cells’
- Clinical context:
- Elderly people
- Left sided
- Segmental on endoscopy
what are complications of ischaemia of large bowel?
massive bleeding, rupture, stricture
how can broad spectrum antibiotics cause ischaemia of bowel?
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
what is collagenous collitis?
= 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
what is lymphocytic collitis?
= 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
what is microscopic colitis?
- 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
what is diverticulitis?
= colon gets outpouching and poo collects in outpouch and can get inflamed or infected (very bad infection if poo pops out)
