Tumours of Lower GIT Flashcards
Where are adenomas commonly found in the small intestines and its appearance?
ampulla of Vater (looks enlarged with a velvety surface)
Where are adenocarcinomas commonly found in the small intestines, what type of mass are they and their appearance?
- duodenum
- polypoid exophytic mass
(napkin-ring encircling pattern)
Describe non-neoplastic and neoplastic tumours in the colon and rectum
- non-neoplastic can be hyperplastic or hamartomatous
- neoplastic adenomas can be tubular (most common), villous or tubulovillous
Where are hyperplastic polyps usually found and what do they look like?
- rectosigmoid colon
- look like nipple-like, hemispheric, smooth, moist, protrusions of the mucosa
Describe the histology of the hyperplastic polyps
- well-formed glands and crypts
- lined with non-neoplastic epithelial cells
- most show differentiation into mature goblet or absorptive cells
- no malignant potential
Describe hamartomatous polyps
- juvenile polyps (usually affects children under 5)
- found in rectum usually
- are malformations of the mucosal epithelium in lamina propria
- Peutz-Jeghers polyps (genetic syndrome)
- stomach, colon or small bowel
- involve mucosal epithelium, lamina propria and muscularis mucosa
Describe the histology of hamartomatous polyps (juvenile polyps)
- abdundant cystically dilated glands
- inflammation
- surface can be congested or ulcerated
- no malignant potential
Describe the histology of hamartomatous polyps (Peutz-Jeghers polyps)
- large and pedunculated
- no malignant potential but increased risk of pancreas/breast/lung/ovary/uterus carcinoma
Neoplastic adenomas can be precursors for cancer, how is risk correlated?
- polyp size:
- rare if tubular adenoma less than 1cm
- high risk if sessile villous adenoma greater than 4cm
- histological architecture
- severity of epithelial dysplasia
Describe the location and morphology of tubular adenomas
- mostly found in colon
- usually less than 2.5cm
- smaller ones tend to be smooth-contoured and sessile
- larger ones tend to be coarsely tubulated and have slender stalks raspberry like
Describe the histology of tubular adenomas
- salk of fibromuscular tissue and prominent blood vessels
- low-grade dyspalstic epithelium that lines glands as tall hyperchromatic, disordered epithelium
- can contain mcin vacuoles
Describe the location and morphology of villous adenomas
- mostly rectum and rectosigmoid
- sessile and can be up to 10cm
- velvety or cauliflower like masses
- can project up to 3cm above normal mucosa
Describe the histology of villous adenomas
- villiform extensions of mucosa
- covered in dysplastic, disordered columnar epithelium
What are the 3 things that signify an adequate removal of pedunculated adenoma (stalked)?
- adenocrcinoma is superficial and does not approach margin of excision across base of stalk
- no vascular or lymphatic invasion
- carcinoma not poorly differentiated
What kind of polyps do patients with FAP syndrome tend to develop?
tubular adenomas
What are the dietary risk factors of colorectal cancer?
- excess caloric intake relative to requirements
- low content vegetable fibre
- high content refined carbohydrates
- intake of red meat
- decreased intake of protective micronutrients
What are the most common sites of colorectal adenocarcinomas?
- rectosigmoid colon (55%)
- caecum/ascending colon (22%)
- transverse colon (11%)
- descending colon (6%)
- other sites (6%)
Describe the morphology of tumours found in the proximal colon
- polypoid, exophytic masses
- obstruction uncommon
- penetrates bowel wall as subserosal and serosal white, firm masses
Describe the morphology of tumours found in the distal colon
- annular, encircling lesions
- margins heaped up, beaded and firm
- mid region is ulcerated
- lumen narrowed
- possible distension of proximal bowel
- penetrates the bowel as subserosal and serosal white firm masses
Describe the histology of colorectal adenocarcinomas
- can range from tall columnar cells resembling the adenomatous lesion counterpart
- to undifferentiated, anaplastic (poorly differentiated) masses
- may produce mucin
- invasive tumour incites srtong desmoplastic stromal response (adhesions or fibrous connective tissue within a tumour)
Describe the clinical symptoms of colorectal cancer
If caecum and right colonic:
- fatigue
- weakness
- iron-deficiency anaemia
If left sided lesion:
- occult bleeding
- changes in bowel habit
- crampy left lower quadrant discomfort
Describe Dukes’ Staging of colorectal cancer
A) confined to submucosa or muscle layer
B) spread through the muscle layer but no involvement of lymph nodes yet
C) involvement of lymph nodes
What are carcinoid tumours?
tumours derived from endocrine cells
What factors determine the aggression of carcinoid tumours?
- site of origin
- depth of local penetration
- size of tumour
- histological features of necrosis and mitosis
Describe the morphology and location of carcinoid tumours
- usually solitary lesion
- mostly found in appendix (or small intestine, rectum etc)
- intramural or submucosal masses that create small polypoid or plateau-like elevations
- colid, yellow-tan appearance on transection
Describe the histology of carcinoid tumours
- neoplastic cells may form discrete islands, trabecular, stands, glands or undifferentiated sheets
- tumour cells uniformly similar
- scant pink granular cytoplasm, and round to oval stippled nucleus
Describe carcinoid syndrome
- cutanous flushes
- apparent cyanosis
- diarrhoea, cramps, nausea, vomiting
- cough, wheeze, dyspnoea
What are the GI lymphomas?
B-cell lymphomas:
- MALT (in stomach, small intestine, proximal colon and distal colon)
- immunoproliferative small intestinal disease
T-cell lymphomas:
- associated with long-standing malabsorption syndrome
- poor prognosis
Describe mesenchymal tumours
- lipomas (firm nodules arising within submucosa or muscularis propria)
- leiomyomas
- leiomyosarcomas (large, bulky intramural masses that fungate and ulcerate into lumen or project subserosally into abdo space)
Describe tumours of the anal canal
- warts commonest benign neoplasm
Carcinomas:
- basoloid pattern (immature proliferative cells derived from basal layer of stratified squamous epithelium)
- squamous cell carcinoma (closely associated with chronic HPV infection)
- adenocarcinoma (extension of rectal adenocarcinoma)
- malignant melanoma
