Polyps Flashcards
What is a polyp?
Protrusion of tissue into lumen above surrounding intestinal mucosa
How are colorectal polyps classified?
- by their morphologic/endoscopic appearance (Paris classification)
- pedunculated, sessile, flat, depressed
- by histology
- non-neoplastic
- hyperplastic
- inflammatory
- inflammatory pseudopolyps
- prolapse-type inflammatory polyps
- hamartomatous
- juvenile polyps
- Peutz-Jeghers polyps
- Conkhite-Canada syndrome
- PTEN hamartoma tumour syndrome
- neoplastic
- serrated polyps
- (hyperplastic polyps are serrated but non-neoplastic)
- TSAs
- SSA/Ps +/- dysplasia
- traditional adenomatous polyps
- tubular, tubulovillous or villous +/- dysplasia
- malignant polyps
- serrated polyps
- non-neoplastic
What are inflammatory pseudopolyps?
Non-neoplastic intraluminal projections consisting of epithelial and stromal components plus inflammatory cells. They are irregularly shaped islands of residual intact mucosa that are the result of mucosal ulceration and regeneration that occurs in response to localised or diffuse inflammation (eg UC or Crohn’s).
What are prolapse-type inflammatory polyps?
Result from traction, distortion & twisting of mucosa caused by peristalsis-induced trauma –> localised ischaemia & lamina propria fibrosis. Eg seen in rectal prolapse.
What are hamartomatous polyps?
Made up of tissue elements normally found at that site but growing in a disorganised mass.
May be sporadic but more commonly seen in genetic syndromes eg Peutz-Jeghers, juvenile polyposis and PTEN hamartoma syndrome.
Sporadic juvenile polyps of colon occur in up to 2% of chidlren <10yrs - usu solitary, not assoc w increased CRC (isolated ones most common in rectosigmoid).
Juvenile polyposis syndrome = autosomal dominant condition characterised by multiple hamartomatous polyps throughout GI tract - at increased risk for colorectal & gastric cancer.
PTEN hamartoma tumour syndrome = primarily composed of Cowden & BRRS syndrome; due to mutation in PTEN gene.
What are hyperplastic polyps?
A form of serrated polyp. They are the most common type of non-neoplastic polyp in the colon; don’t appear to have malignant potential but may be associated with an increased risk of proximal neoplasia. Histologically they have a characteristic ‘saw tooth’ pattern and can be difficult to distinguish from SSA/P.
What are sessile serrated adenomas?
- A form of serrated polyp
- More prevalent in the proximal colon
- Have a smooth surface sometimes with a ‘cloud-like’ appearance, often flat/sessile & may be covered with mucus
- May acquire dysplasia
SSPs, particularly those with dysplasia, are considered the likely precursers of sporadic MSI-H colon ca through a molecular pathway characterised by a high frequency of methylation of some CpG islands (CIMP-positive) - may result in hypermethylation of the promoter region of MMR MLH1 & silencing of gene expression. Activation of the BRAF oncogene (BRAF V600E mutation) = also a feature of SSA/Ps, as well as many hyperplastic polyps
What are traditional serrated polyps?
- A form of serrated polyp
- More prevalent in the rectosigmoid colon
- May be flat or pedunculated
- Have diffuse but often mild dysplasia
What is serrated polyposis syndrome?
A rare condition characterised by multiple large and/or proximal serrated polyps. These patients carry an increased risk of CRC; the lifetime risk is unknown but the 5year risk while under surveillance is 1%.
Diagnosed by the WHO criteria:
- At least 5 serrated polyps proximal to the rectum all ≥5mm, with at least 2 ≥10mm
OR
- >20 serrated polyps of any size but distributed throughout the large bowel, with ≥5 proximal to the rectum
(Any histological subtype is included and the diagnosis may require >1 colonoscopy; polyp count cumulative over time.)
How common are adenomatous polyps and what are the risk factors for these?
What are some endoscopic features suggestive of invasive cancer?
- Commonest type of colonic polyp - account for > 2/3
- 25% by age 50, 50% by age 70
- Risk factors: increasing age, BMI, lack of exercise, male
Only a small minoirty (≤5% over 7-10yrs) progress to ca but risk is higher if HGD, ≥10mm or villous component.
Endoscopic features suggestive of invasive carcinoma include friability, induration and ulceration.
What is the Paris classification?
The Paris classification of superficial gastrointestinal neoplastic lesions:
- 0-I Polypoid:
- 0-Ip: protruded, pedunculated
- 0-Is: protruded, sessile
- 0-II Nonpolypoid:
- 0-IIa: slightly elevated
- 0-IIb: flat
- 0-IIc: slightly depressed
- 0-III Excavated
What are the different histological types of adenomatous polyps?
Advanced adenoma = ≥10mm, villous component or HGD
Tubular adenoma = >80% adenomas, need ≥75% tubular component (branching, adenomatous epithelium)
Villous adenoma = 5-15% adenomas, need ≥75% villous component (long glands extending straight down from surface to centre of polyp)
Tubulovillous = 5-15%, have 25-75% villous features
Some degree of dysplasia in all polyps:
- LGD
- HGD/intraepithelial carcinoma (no invasion through BM)
- carcinoma in situ (invasion into LP but don’t penetrate MM)
- invasive adenocarcinoma (extends through MM and beyond)
What is the endoscopic management of polyps?
Adenomatous polyps
- if ≤2mm may be completely removed w biopsy forceps
- otherwise snare +/- electrocautery or advanced techniques (EMR/ESD)
- large sessile ones often need piecemeal resection
- otherwise surgery
- pedunculated polyps w features of deep submucosal invasion - polypectomy with en bloc resecton
- nonpedunculated polyps w features of deep submucosal invasion - biopsy area of surface feature disruption, tattoo if polyps not at or near caecum & refer for surgical mx
- these polyps should be resected en bloc rather than piecemeal
Serrated polyps ≥5mm should be completely resected
What are the categories of polyp risk?
-
Average risk polyps
- Conventional adenomas
- tubular adenoma <10mm
- Serrated polyps
- SSA/P <10mm
- Hyperplastic polyp ≥10mm (f/u as high risk polyp if concern re distinguishing from SSP)
- Conventional adenomas
-
High risk polyps
- Conventional adenomas (these are advanced adenomas)
- adenoma ≥10mm
- adenoma w villous or tublovillous histo (>25% villous histo)
- adenoma w HGD
- Serrated polyps
- SSA/P ≥10mm
- SSA/P w HGD
- TSA
- Serrated adenoma, unclassified
- Conventional adenomas (these are advanced adenomas)
What is the recommended follow-up after polyp excision in the absence of a known familial disorder/family history concerns?
- after piecemeal resection of polyps ≥20mm, site should be checked within 2-6mo then additional colonoscopy after further 12mo
- once no recurrence confirmed, surveillance after further 3yrs; then need for further durveillance determined in accordance w this update & individual virus factors
- no surveillance for hyperplastic polyps ≤10mm unless meets criteria for serrated polyposis syndrome
Surveillance intervals:
-
Adenomas
-
1 year:
- ≥10 adenomas (consider ref to NZFGCS)
- 3yrs:
- 5-9 adenomas <10mm
- 1 advanced adenoma
- 5yrs:
- 3-4 adenomas <10mm
- 10yrs or NZBSP (whichever first)
- 1-2 adenomas <10mm
-
1 year:
-
Serrated polyps
- 1year:
- SPS - initial interval after polyp clearance (consider ref to NZFGCS)
- 3yrs:
- ≥5 SSA/P <10mm
- SSA/P ≥10mm
- SSA/P w dysplasia
- TSA
- 5yrs
- 1-4 SSA/P <10mm
- HP ≥10mm (3yrs if concern re differentiating from SSA/P)
- 1year:
If >75yrs, or significant comorbidities, consider risks & benefits - only survey if >10yrs life expectancy