Colorectal polyps

Section: Colorectal Sub-section: Colorectal cancer Curriculum: Curriculum, page 21

Sessile serrated lesions

• Hyperplastic polyps
  • Small rectal HP are not associated with increased risk of cancer.
  • Distal HP may be associated with a small risk
• Sessile serrated polyps/adenoma
  • Increased risk of cancer and therefore managed like adenomas
• Serrated polyposis syndrome
  • May carry a mutation in rare polyposis-associated genes including SMAD4, BMPR1A, PTEN, GREM1, RNF43, and MUTYH, these genes are not altered in the majority of individuals with SPS
  • Significantly increased risk of CRC (20%)

Adenomatous polyps

Epidemiology:

• 2/3 of colonic polyps are adenomas Risk factors:
• Age
• Obesity
• M>F Clinical features:
• General asymptomatic, most detected by colon cancer screening tests
• Small adenomas do not typically bleed Endoscopic features:
• Majority are <1 cm
• Adenomas may be: o Sessile – base & top of lesion have same diameter o Pedunculated – base is narrow with mucosal stalk interposed between polyp and wall o Flat o Depressed
• Features suggestive of malignancy include friability, induration, ulceration, adherence to underlying tissue.

Adenoma-carcinoma sequence:

• Observational data supporting this hypothesis: o Early carcinomas are frequently seen within large adenomatous polyps. Areas of adenomatous change are often found surrounding CRC. o Adenomas and carcinomas are found in similar distributions throughout the large bowel o Adenomas are typically observed 10-15 years prior to the onset of cancer in both sporadic and familial cases o Ability to reduce the incidence of CRC through removal of polyps has been shown in controlled trials
• Genetic basis: o Accumulation of mutations (germline or somatic) causes malignant transformation. o Mutations of APC usually occur early, leading to formation of early adenomas, whereas p53 generally occurs late, with transformation of adenoma to carcinoma.

Malignant polyp:

• Definition: Polyp containing adenocarcinoma with breaching the muscularis mucosae
• If suspicion of possible malignancy in polyp, site should be tattooed.

Clinical/endoscopic assessment

• Macroscopic assessment
  • Paris classification
    • Vertical growth pattern, less likely to be invasive Ip and Is
    • Flat are moderate increased risk, maybe high grade adenoma.
    • Lateral spreading tumours LST. Paris II
      • Homogenous type – low risk 0.5% SMI
      • Nodular mixed and pseudo depressed type have high risk of deep SMI
    • Depressed are high risk for carcinoma, Paris III
• Signs of concerning lesions -should biopsy but not try endoscopic resection.
  • Non-lifting sign – should not have to do in first place
  • Fold convergence
  • Demarcated depressed area
  • Stalk or base swelling
  • Spont bleeding
  • Chicken skin appearance
• Microscopic assessment
  • Narrow band imaging – can use different wavelengths to highlight surface epithelial and underlying vessel features
    • NBI International colorectal endoscopic (NICE) classification
    • Type 1 to 3
      • Colour, light to brown
      • Vessels, none to disrupted
      • Surface pattern
        • Most likely pathology: hyperplasic, adenoma or deep submucosal invasive cancer.

Histological assessment

• Risk stratification based on pathology
  • Level of invasion
    • Pedunculated: Haggitt classification level 1-4: head, neck, stalk or base
      • Risk in 0-III <1%, risk in IV is 25%
    • Sessile: Kikuchi classification sm1-3: level of submucosa depth by thirds. Risk of nodal mets 2, 8 and 23% respectively.
      • Sm1 local excision adequate
      • Sm2/3 not recommended for local excision
    • Note : 1mm submucosal invasion is often used instead of the above (given you need some muscularis propria in order to properly use Kikuchi)
  • Margin status
    • If < 1 mm, then treat as positive. Risk of residual disease 21-33%.
  • Polyp architecture
    • Risk of underlying malignancy by architectural variants
      • Villous polyps 10%-18%
      • Tubulovillous 6%-8%
      • Tubular polyps 2%-3%
  • Adverse features:
    • Poor differentiation
    • Lymphovascular invasion
    • Tumour budding
• Piecemeal resection
  • may be unreliable margin.

Histological feature	Grade of risk	Estimated risk of residual disease
Resection margin < 1 mm	Very high	20%
Pedunculated Haggitt level 4	Very high	20%
Kikuchi sm3	Very high	20%
Poor differentiation	High	8–15%
Kikuchi sm2	Medium	5–10%
Lymphovascular invasion	Medium	5–10%
Resection margin 1–2 mm	Low	5%
Tumour budding	Low	5%

Surveillance after adenoma

-        Very low risk: 1-2 adenomas < 1 cm repeat in 10 years -        Low risk: 3-4 adenomas -        Intermediate: 5-9 adenomas or at least 1 > 1 cm, or TV or villous adenoma or HGD  repeat in 3 years -        High risk: > 10 adenomas, or 3+ with 1 > 1 cm  repeat in 1 year

Polyp classificaion

Paris classification

Kudo classification

NICE NBI classification

Source: Colorectal polypectomy and endoscopic mucosal resection- European Society of Gastrointestinal Endoscopy (ESGE) Guideline

Endoscopic mucosal resection

• Inject beneath the lesion to lift it and separate it from the muscularis propria.
  • Use a needle to inject a solution, typically saline or a mixture with epinephrine (to reduce bleeding) and a dye like methylene blue or indigo carmine (to visualize the lift).
  • Ensure an adequate and uniform submucosal cushion is created (“the lift”).
• Resection
  • Snaring:
    • Use a snare to encircle the lesion.
    • Position the snare around the elevated lesion and close it gently to capture the base of the lesion.
  • Electrocautery:
    • Apply electrocautery energy to cut and cauterize simultaneously. Settings depend on lesion location and equipment.
    • Resect in piecemeal fashion for larger lesions (piecemeal EMR) or en bloc for smaller lesions.

Endoscopic submucosal dissection

• Define the borders:
  • Use the ESD knife or argon plasma coagulation to mark the perimeter of the lesion at least 5mm beyond its visible margin.
  • This ensures clear margins during dissection.
• Create a submucosal cushion:
  • Inject a solution (e.g., saline, glycerol, hyaluronic acid, or a mixed solution with epinephrine and indigo carmine).
  • This separates the lesion from the muscularis propria, facilitates dissection, and reduces the risk of perforation.
  • Reinject as needed during the procedure.
• Circumferential mucosal incision:
  • Use the ESD knife to incise the mucosa around the marked borders.
  • Start with a small incision and extend it to encircle the lesion completely.