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Path - Tumours of Small + Large Intestines (i) (BowelScreen (est in 2012,…
Path - Tumours of Small + Large Intestines (i)
primary tumours
non-neoplastic polyps
epithelial neoplasms
benign adenomatous polyps
malignant: adenocarc, carcinoid
mesenchymal neoplasms
lymphoma
Secondary tumours
rare
ovarian
melanoma
endometrial carc
prostatic carc
tumours of large bowel more common than tumours of small bowel
polyps
mass arising from the mucosal epithelium or from the submucosal connective tissue protruding into the lumen of the gut
non-neoplastic polyps
hyperplastic (metaplastic polyps)
common
in >50% of over 60s
often in recto-sigmoid colon
<5mm
single or multiple
asymptomatic
composed of non-neoplastic glands with goblet cell differentiation + serrated appearance (sawlike jagged edge)
results from delayed shedding of surface epithelial cells
virtually no malignant potential
hamartomatous polyps
disorganised tissue normal to site
juvenile polyps
hamartomatous malformations of bowel mucosa
in children <5 but can be encountered in adults (name changes to retention polyps)
rectum
can be large (1-3 cm)
cystically dilated glands in an inflamed stroma
no malignant potential (i.e. the polyps themselves will not become cancerous)
Peutz-Jeghers
hamartomatous polyps of SI + colon
single = PJ polyp
multiple = PJ syndrome (PJS)
AD
mucocut pigmentation around lips, oral mucosa, genitalia + palmar surfaces of the hand
polyps have no malignant potential but patients have increased risk of developing GI + non-GI cancers (pancreas, breast, lung, ovary, uterus)
glands + connective tissue with smooth muscle
resemble xmas tree
Cowden syndrome
AD mutation in PTEN gene
multiple hamartomatous polyps + trichoepitheliomas (benign skin lesions that originate from hair follicles)
no malignant potential but the patients have increased risk of developing thyroid + breast cancer
Cronkhite-Canada syndrome
hamartomatous polyps, nail atrophy, skin pigmentation
inflamm (pseudo) polyps
inflamed regenerative mucosa surrounded by ulcerated tissue
seen in patients with longstanding IBD
lymphoid polyps (intramucosal lymphoid tissue)
neoplastic polyps
= adenomas (adenomatous polyps)
common (prevalence = 50% @ age 60)
prolif of dysplastic epithelium (ranges from mild to severe)
carc precursors
benign - may process via the adenoma-carcinoma sequence
3 types
tubular - usually pedunculated
villous - usually sessile, tend to progress to carc more
tuboluvillous (mix)
all are covered by dysplastic epithelium
risk of malignancy correlates with size (>2cm), histological type (villous component) + degree to dysplasia
since they are considered premalignant all should be removed
may be asymp - incidental find on colonoscopy
may present with occult bleeding, anaemia, protein loss + obstruction
Tx = complete excision
FAP
AD
Familial adenomatous polyposis
mutations of APC gene on chromo 5q21
numerous adenomatous polyps throughout GIT (esp large bowel)
min for dx = 100 (may be >2000)
average age of onset of polyps = teens-20s (bleeding + anaemia)
virtually 100% risk of carc (within 10-15 yrs) - indication for prophylactic total colectomy
Gardner's syndrome
variation of FAP
mutations of APC gene
AD
multiple adenomas but also epidermoid cysts (skin), fibromatosis (soft tissue), osteomas (bone), abnormal dentition (teeth)
Turcot's syndrome
variation of FAP
AD
mutations of APC gene
CR adenomas polyps + brain tumours (gliomas, medulloblastoma)
pedunculated (stalk) or sessile (flat)
BowelScreen
est in 2012
target pop = 60-69 yrs (will expand to incl 55-74)
offered screening every 2 yrs
home test kit
Faecal immunochemical test (FIT)
detects occult blood
polyps are usually clinically silent, but can bleed
anyone +ve invited to colonoscopy
aim = to remove adenomatous polyps before progression to carc
all polyps removed + examined microscopically