Gastrointestinal Pathology Flashcards
What is the basic histopathological structure of the GIT?
Mucosa = epithelium, lamina propria and muscularis mucosa
Submucosa
Muscularis propia = inner circular layer and outer longitudinal layer.
Submucosal plexus found in the submucosal layer
The myenteric plexus found between the muscular layers.
What are the key histological features of the duodenum?
Brunners glands in the submucosal layers
What special stain is used to identify the glandular/goblet cells of the large intestine?
Alcian blue (mucus = goblet cell) / Van Gieson stain (firbous/collagen)
A 70yr old male presents with chronic left sided abdominal pain and changing bowel habits, sometimes reports blood in his stool. pMH diabetes mellitus, internal haemorrhoids, HTN Colonscopy biopsy shows:
What is the most likely diagnosis?
Diverticulosis - not the pouching of mucosa through the muscularis layers.
What are the key epidemiology of inflammatory bowel disease?
More common in males - adolscent/young then second peak in 5th decade
Northern latitidue
White
Associated with VitD deficiency
What are the defining features of Crohns disease?
Abdominal pain
Fever
Diarrhoea
No blood or mucus
Entire GIT involved
Skip lesions on endoscopy
Transmural and terminal ileum
Smoking is a risk factor
What are the defining symptoms of ulcerative colitis?
Bloody diarrhoea
Mucus
Abdominal pain
Continuous
Lower colon and rectum only
Only sumbmucosal
Smoking protective
Excrete blood and mucus
Use aminosalicylates
Protective smoking
What defects in the immune system can predispose someone to Crohns disease?
NOD2 suspectibility - binds to intracellular bacterial peptidogylcans - when faulty allows bacteria to enter intestinal epithelium
Defect in epithelial tight junctions
Defects in regulatory T cells, especially IL-10 producing
Variation in gut microbiota
What are the gross features of crohns disease on a specimen?
Cobblestone appearance to mucosa
Creeping fat/fat wrapping
Thickened fibrotic/white bowel wall
May identify strictures and fistulas
What are the key microscopic features of crohns disease on histology?
Ulceration - deep with normal tissue on either side
Transmural inflammation - immune cells throughout the GIT wall
Crypt absess - crypt overflowing with immune cells
Non ceasating granulomas
What are the gross pathological features of ulcerative colitis on specimen?
Diffusely abnormal granular mucosa
Pseudopolyp
Thinning of the bowel wall
Mucus plugs
What are the microscopic features of ulcerative colitis on histology?
Inflammation cryptitis and crypts abscess
No granulomas
Inflammation limited to mucosa and submucosa
Pseudopolyps
Broad based ulcers
What extra-GIT manifestations are more common in crohns disease?
Nephrolithiasis (inc oxalate absoprtion)
Cholelithiasis
Metabolic bone disease (LOW Vit D)
Arthiritis
Apthous ulcers
Episcleritis
Perianal disease
Erythema nodosum
Anal involvement
What extra-GIT/indirect features are more common in ulcerative colitis?
Pyoderma gangrenosum
PSC
Anemia
Malignancy more common
What is the most common malignancy of the GIT?
Adenocarcinoma
What are the two different FAP variants?
Gardner syndrome - osteomas of mandible, skull, long bones, thyroid tumours, dental problems and epidermal cysts
Turcot syndrome - rarer, instetinal adenomas and CNS tumours
What type of adenoma tends to be found in Lynch syndrome?
Sessile serrated adenomas
What genes are located in Lynch syndrome?
MLH-1
PMS2
MSH2
MSH6
What are the two genetic pathways by which colorectal cancer can develop?
- Classic adenoma carcinoma sequence
- Microsatellite instability pathway
What are the key features of the classic adenoma carcinoma sequence for the development of colorectal cancer?
Acquired accumulation of genetic mutations - APC, RAS, p53 are key.
Chromosomal instability
Microsatellite stability
Typically leads to tubular adenoma that develops into a carcinoma.
Typically point mutations
What are the key features of microsatellite instability pathway as a way of developing colorectal cancer?
Microsatellite instability due to failure in mismatch repar genes - typically associated with Lynch Syndrome (MLH1 or MSH2)
Forms a sessile serated adenoma which later becomes a carcinoma.
Rarer
What is the signet ring sign for colorectal adenocarcinoma?
Nucleus is pushed to the side by the mucus accumulating inside the cell.
