Colonic Polyps

1. Clinical Overview

Summary

Colonic polyps are abnormal tissue growths that protrude from the colonic mucosa into the bowel lumen. They represent a heterogeneous group of lesions with varying malignant potential, ranging from benign hyperplastic polyps to premalignant adenomas that serve as precursors to the majority of colorectal cancers (CRC).[1,2]

The clinical significance of colonic polyps lies in their role as the primary target for colorectal cancer prevention. The adenoma-carcinoma sequence, first described by Vogelstein and colleagues, demonstrates that approximately 70-90% of sporadic colorectal cancers arise from adenomatous polyps through a stepwise accumulation of genetic mutations over 10-15 years.[3] This long dwell time provides a critical window for intervention through colonoscopic surveillance and polypectomy.

Polyps are extremely common, with autopsy studies demonstrating prevalence rates of 30-50% in individuals over 50 years of age in Western populations.[4] However, only a minority (approximately 5-6%) of adenomas will progress to invasive carcinoma, making risk stratification essential to optimise surveillance resources while ensuring high-risk individuals receive appropriate follow-up.[5]

The introduction of population-based bowel cancer screening programmes has dramatically increased polyp detection rates. In the UK, the NHS Bowel Cancer Screening Programme utilises faecal immunochemical testing (FIT) followed by colonoscopy for positive results, with adenoma detection rates of 12-15% in the screening population.[6] Understanding polyp classification, risk stratification, and evidence-based surveillance intervals is therefore essential for all clinicians involved in gastroenterology and colorectal practice.

Key Facts

Clinical Pearls

"The Adenoma-Carcinoma Sequence is the Cornerstone" The majority of colorectal cancers (70-90%) arise from adenomatous polyps through sequential genetic mutations. This 10-15 year window for intervention makes colonoscopic surveillance one of the most effective cancer prevention strategies available.[3]

"Villous = Vicious" Villous adenomas carry the highest malignant potential among adenoma subtypes. A villous adenoma > 2cm has a 17-40% chance of harbouring invasive carcinoma. Size, villous histology, and high-grade dysplasia are the key determinants of risk.[7]

"Right-Sided Serrated Lesions Are Dangerous and Easily Missed" Sessile serrated lesions (SSLs) in the proximal colon are often flat, pale, and covered with mucus, making them notoriously difficult to detect. They follow an alternative molecular pathway (BRAF mutation, MLH1 hypermethylation) to MSI-high cancers and may have accelerated carcinogenesis.[8,12]

"Not All Polyps Need Surveillance" Low-risk adenomas (1-2 small tubular adenomas with low-grade dysplasia) do not require surveillance colonoscopy — patients should return to population screening. Surveillance is reserved for intermediate and high-risk findings.[13]

"FAP = Prophylactic Colectomy" Familial adenomatous polyposis (FAP) caused by germline APC mutations leads to 100% colorectal cancer risk by age 40-50. Prophylactic proctocolectomy is indicated, typically by age 25 or when polyp burden becomes unmanageable.[9]

"Lynch Syndrome — Think MSI-High" Hereditary non-polyposis colorectal cancer (Lynch syndrome) results from mismatch repair gene mutations. Cancers are MSI-high, often right-sided, and respond well to immunotherapy. Intensive surveillance from age 25 is essential.[10]

Why This Matters Clinically

Colonic polyps are the most important target for colorectal cancer prevention worldwide. The National Polyp Study demonstrated that colonoscopic polypectomy reduces colorectal cancer incidence by 76-90% and mortality by 53%.[11,14] Accurate histological assessment, appropriate risk stratification, and evidence-based surveillance intervals are essential competencies for gastroenterologists, surgeons, and all clinicians involved in bowel cancer screening.

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2. Epidemiology

Incidence & Prevalence

Colonic polyps are among the most common gastrointestinal lesions, with prevalence increasing significantly with age. Geographic variation exists, with higher rates in Western countries correlating with dietary and lifestyle factors.[4]

Risk Factors

Protective Factors

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3. Pathophysiology

The Adenoma-Carcinoma Sequence (Vogelstein Model)

The adenoma-carcinoma sequence, elucidated by Fearon and Vogelstein in 1990, describes the stepwise genetic progression from normal colonic epithelium to invasive carcinoma through accumulation of specific mutations.[3]

Chromosomal Instability (CIN) Pathway — "Classical" Pathway

This pathway accounts for approximately 70-85% of sporadic colorectal cancers and is characterised by chromosomal instability with widespread loss of heterozygosity (LOH).

Key Molecular Players:

Timeline: The adenoma-carcinoma transition typically requires 10-15 years, providing the rationale for screening and surveillance intervals.[3,5]

The Serrated Pathway (Alternative Pathway)

The serrated neoplasia pathway represents an alternative route to colorectal carcinogenesis, accounting for 15-30% of sporadic CRC. It is characterised by BRAF mutation, CpG island methylator phenotype (CIMP), and microsatellite instability (MSI).[8,12]

Characteristics of Serrated Pathway Cancers:

• Predominantly right-sided (proximal colon)
• MSI-high phenotype (15-20% of sporadic CRC)
• Often poor differentiation with mucinous features
• Better prognosis stage-for-stage than MSS cancers
• Responsive to immune checkpoint inhibitors [8,12]

Clinical Implications:

• SSLs are often flat, pale, and covered with mucus
• Easily missed at colonoscopy (miss rate up to 20-30%)
• May have accelerated progression ("interval cancers")
• High-definition colonoscopy and chromoendoscopy improve detection [12]

Mismatch Repair Deficiency Pathway (Lynch Syndrome)

Lynch syndrome results from germline mutations in DNA mismatch repair (MMR) genes, leading to microsatellite instability and accelerated carcinogenesis.[10]

Characteristics:

• MSI-high phenotype
• Right-sided predominance
• Younger age of onset (mean 44 years)
• Multiple synchronous/metachronous cancers
• Better prognosis than sporadic MSS cancers
• Lynch-associated CRCs respond to immunotherapy [10]

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4. Classification of Colonic Polyps

Histological Classification (WHO 2019)

Colonic polyps are classified based on histological features into neoplastic and non-neoplastic categories.[7]

Adenomatous Polyps (Conventional Pathway)

Risk Factors for Malignant Transformation:

Serrated Lesions (Updated WHO 2019 Terminology)

The WHO 2019 classification updated terminology for serrated lesions:[7,12]

Histological Features of SSL:

• Horizontally branching (L-shaped or inverted T-shaped) crypts at base
• Crypt dilation and irregular serration
• Crypt base extension along muscularis mucosae
• Absent or minimal cytological dysplasia (until advanced)
• BRAF mutation positive (~80%)
• MLH1 promoter hypermethylation when progressing

Hamartomatous Polyps

Paris Classification (Endoscopic Morphology)

Dysplasia Grading

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5. Clinical Presentation

Symptoms

The majority of colonic polyps are asymptomatic and detected incidentally during screening or investigation for other conditions. Symptomatic presentation is more common with large polyps (> 2cm) or those in the rectum.[1,2]

McKittrick-Wheelock Syndrome: A rare but important clinical entity caused by large secretory villous adenomas (usually rectal), resulting in:

• Profuse mucous diarrhoea (> 1-3L/day)
• Severe hypokalaemia
• Hyponatraemia
• Dehydration
• Pre-renal acute kidney injury Management requires urgent resection with aggressive electrolyte replacement.[23]

Signs

Red Flags — Urgent Investigation Required

[!CAUTION] Red Flags Requiring Urgent Referral (2WW Pathway):

• Rectal bleeding with change in bowel habit (> 40 years)
• Unexplained iron deficiency anaemia
• Palpable abdominal or rectal mass
• Family history suggestive of polyposis syndrome
• FIT positive result

[!CAUTION] High-Risk Polyp Features Requiring Close Follow-up:

• 100 polyps on colonoscopy (consider FAP)

• ≥5 adenomas or any adenoma ≥20mm
• High-grade dysplasia
• Sessile serrated lesion ≥10mm or with dysplasia
• Invasive carcinoma in polyp (pT1)

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6. Clinical Examination

Physical Examination Approach

Most patients with colonic polyps will have an entirely normal physical examination. However, systematic examination is essential to exclude associated malignancy and identify features of polyposis syndromes.

Structured Approach:

1. General inspection:

   • Nutritional status, pallor (anaemia), cachexia (malignancy)
   • Mucocutaneous pigmentation (Peutz-Jeghers)
   • Skin lesions (epidermoid cysts — FAP/Gardner)

2. Abdominal examination:

   • Usually unremarkable
   • Palpable mass (rare — very large polyps or carcinoma)
   • Hepatomegaly (metastatic disease if concurrent malignancy)

3. Digital rectal examination (DRE):

   • Palpable low rectal polyps
   • Rectal mass
   • Blood or mucus on glove

4. Extraintestinal manifestations (polyposis syndromes):

   • Head: Osteomas (mandible, skull — FAP/Gardner)
   • Eyes: Congenital hypertrophy of retinal pigment epithelium (CHRPE — FAP)
   • Mouth: Perioral pigmentation (Peutz-Jeghers), dental abnormalities (FAP)
   • Skin: Epidermoid cysts, desmoid tumours (FAP/Gardner)

Polyposis Syndrome Physical Features

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7. Investigations

Colonoscopy — Gold Standard

Colonoscopy is the gold-standard investigation for polyp detection, characterisation, and removal. It allows direct visualisation, tissue sampling, and therapeutic polypectomy.[1,2]

Enhanced Colonoscopy Techniques

Polyp Characterisation During Colonoscopy

Histopathology — Essential for Risk Stratification

All removed polyps should be sent for histological assessment. The pathology report should include:[7]

Malignant Polyp Assessment (Carcinoma in Polyp)

If invasive carcinoma is identified within a polyp, additional histological features determine management:[25]

Haggitt Classification (Pedunculated Polyps):

Kikuchi Classification (Sessile Polyps — Submucosal Invasion):

CT Colonography (Virtual Colonoscopy)

Investigations for Polyposis Syndromes

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8. Management

Management Algorithm

                    COLONIC POLYP DETECTED
                              ↓
┌──────────────────────────────────────────────────────────────────┐
│                       POLYPECTOMY                                │
├──────────────────────────────────────────────────────────────────┤
│  PEDUNCULATED (0-Ip):                                            │
│  ➤ Hot snare polypectomy (diathermy)                             │
│  ➤ Clip base of stalk if bleeding risk (> 2cm or thick stalk)    │
│                                                                  │
│  SESSILE less than 10
mm:                                                  │
│  ➤ Cold snare polypectomy (preferred for diminutive polyps)     │
│  ➤ Avoids delayed bleeding and post-polypectomy syndrome        │
│                                                                  │
│  SESSILE 10-20
mm:                                                │
│  ➤ En bloc or piecemeal EMR (endoscopic mucosal resection)      │
│  ➤ Consider cold snare piecemeal for appropriate lesions        │
│                                                                  │
│  SESSILE > 20mm (Laterally Spreading Tumours):                    │
│  ➤ EMR (en bloc if possible, piecemeal if necessary)            │
│  ➤ ESD (endoscopic submucosal dissection) for en bloc excision  │
│  ➤ Refer to specialist centre if not amenable                   │
│  ➤ Surgical resection if endoscopic excision not feasible       │
│                                                                  │
│  SEND ALL POLYPS FOR HISTOLOGY                                   │
└──────────────────────────────────────────────────────────────────┘
                              ↓
┌──────────────────────────────────────────────────────────────────┐
│                    HISTOLOGY RESULT                              │
├──────────────────────────────────────────────────────────────────┤
│  NON-NEOPLASTIC (Hyperplastic):                                  │
│  ➤ No surveillance required (distal/small)                      │
│  ➤ Proximal hyperplastic polyps ≥10
mm: consider as serrated     │
│                                                                  │
│  ▼ ADENOMAS — STRATIFY BY BSG 2020 CRITERIA ▼                   │
│                                                                  │
│  LOW-RISK ADENOMA:                                               │
│  ➤ 1-2 adenomas, all less than 10mm, tubular, low-grade dysplasia        │
│  ➤ NO SURVEILLANCE — return to population screening             │
│                                                                  │
│  INTERMEDIATE-RISK ADENOMA:                                      │
│  ➤ 3-4 small adenomas, OR                                        │
│  ➤ Any adenoma 10-19mm                                           │
│  ➤ Surveillance colonoscopy at 3 YEARS                          │
│                                                                  │
│  HIGH-RISK ADENOMA:                                              │
│  ➤ ≥5 adenomas, OR                                               │
│  ➤ Any adenoma ≥20mm, OR                                         │
│  ➤ High-grade dysplasia                                          │
│  ➤ Surveillance colonoscopy at 1 YEAR                           │
│                                                                  │
│  SERRATED LESIONS (BSG 2020):                                    │
│  ➤ Hyperplastic polyps (distal, less than 10mm): No surveillance         │
│  ➤ SSL less than 10mm without dysplasia: 3-year surveillance             │
│  ➤ SSL ≥10mm OR with dysplasia: 1-year surveillance             │
│  ➤ ≥5 serrated lesions proximal to sigmoid: 1-year surveillance │
│                                                                  │
│  PIECEMEAL EXCISION OF LARGE POLYPS:                             │
│  ➤ Site check at 2-6 months to ensure complete excision         │
│  ➤ Then risk-stratified surveillance                            │
└──────────────────────────────────────────────────────────────────┘
                              ↓
┌──────────────────────────────────────────────────────────────────┐
│              MALIGNANT POLYP (Carcinoma in Polyp)                │
├──────────────────────────────────────────────────────────────────┤
│  ASSESS RISK FEATURES (Haggitt/Kikuchi):                         │
│                                                                  │
│  LOW-RISK — Polypectomy may be curative:                         │
│  ➤ Well or moderately differentiated                            │
│  ➤ No lymphovascular invasion                                   │
│  ➤ Clear margin (≥1mm)                                          │
│  ➤ Sm1 invasion (sessile) or Haggitt 1-3 (pedunculated)        │
│  ➤ Low tumour budding                                           │
│  ➤ Management: Surveillance colonoscopy at 3 months, then 1 year │
│                                                                  │
│  HIGH-RISK — Surgical resection recommended:                     │
│  ➤ Poorly differentiated                                        │
│  ➤ Lymphovascular invasion present                              │
│  ➤ Margin less than 1mm or involved                                      │
│  ➤ Sm2/Sm3 invasion (sessile) or Haggitt level 4 (pedunculated) │
│  ➤ High-grade tumour budding                                    │
│  ➤ Management: MDT discussion → Segmental colectomy             │
│                                                                  │
│  ➤ ALL MALIGNANT POLYPS REQUIRE MDT DISCUSSION                  │
│  ➤ CT staging prior to surgical decision                        │
│  ➤ Consider patient fitness and preference                      │
└──────────────────────────────────────────────────────────────────┘

BSG Post-Polypectomy Surveillance Guidelines (2020)

The British Society of Gastroenterology (BSG) 2020 guidelines provide evidence-based surveillance intervals based on baseline colonoscopy findings.[13]

Serrated Lesion Surveillance (BSG 2020):

Key Changes from Previous Guidelines:

1. Low-risk adenomas no longer require surveillance
2. Reduced surveillance burden (fewer colonoscopies)
3. Serrated lesions explicitly addressed
4. Two surveillance episodes then stop (if clear), unless ongoing high-risk findings

ESGE Polypectomy and Surveillance Guidelines

The European Society of Gastrointestinal Endoscopy (ESGE) provides complementary guidance:[26]

Polypectomy Techniques

Management of Polyposis Syndromes

Familial Adenomatous Polyposis (FAP)

Attenuated FAP

Lynch Syndrome (HNPCC)

Peutz-Jeghers Syndrome

Juvenile Polyposis Syndrome

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9. Complications

Complications of Colonic Polyps

Complications of Polypectomy

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10. Prognosis & Outcomes

Polyp Progression Risk

Outcomes After Polypectomy

Colonoscopy Quality and Outcomes

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11. Polyposis Syndromes — Detailed Overview

Familial Adenomatous Polyposis (FAP)

Genotype-Phenotype Correlations:

Lynch Syndrome (HNPCC)

Amsterdam II Criteria (Clinical Diagnosis):

• ≥3 relatives with Lynch-associated cancer (CRC, endometrial, small bowel, ureter, renal pelvis)
• One is first-degree relative of the other two
• ≥2 successive generations affected
• ≥1 diagnosed before age 50
• FAP excluded

Revised Bethesda Guidelines (For MSI Testing):

• CRC diagnosed less than 50 years
• Synchronous or metachronous Lynch-associated cancers
• CRC with MSI-high histology less than 60 years
• CRC with ≥1 first-degree relative with Lynch-associated cancer less than 50 years
• CRC with ≥2 first/second-degree relatives with Lynch-associated cancer at any age

Peutz-Jeghers Syndrome (PJS)

Juvenile Polyposis Syndrome (JPS)

MUTYH-Associated Polyposis (MAP)

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12. Evidence & Guidelines

Key Guidelines

Landmark Studies

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13. Patient/Layperson Explanation

What Are Colonic Polyps?

Polyps are small growths on the inner lining of your large bowel (colon and rectum). They are very common — about 1 in 4 people over 50 have them. Most polyps are harmless and cause no symptoms at all.

However, some types of polyps (called adenomas) can slowly change and become bowel cancer over many years if left untreated. Removing these polyps during a colonoscopy prevents this from happening.

How Are Polyps Found?

Most polyps are found in one of three ways:

1. Bowel cancer screening — The NHS offers a stool test (FIT) to everyone aged 60-74 (soon 50-74). If positive, you'll have a colonoscopy.
2. Colonoscopy — A camera test to look inside your bowel. Polyps can be seen and removed during this test.
3. Investigation for symptoms — If you have bleeding, change in bowel habit, or anaemia.

What Happens When a Polyp Is Found?

During colonoscopy, the doctor will remove most polyps immediately using a wire loop (called a snare). This is painless. The polyp is sent to the laboratory to determine what type it is.

Do I Need Follow-up After Polyps Are Removed?

It depends on what type, how many, and how large your polyps were:

What If I Have Many Polyps or a Strong Family History?

If you have many polyps (especially > 10) or a strong family history of bowel cancer, you may need:

• Genetic testing to check for inherited conditions
• More frequent colonoscopies
• Family members may also need screening

Your doctor will refer you to a specialist genetics clinic if needed.

Can Polyps Be Prevented?

You can reduce your risk by:

• Not smoking
• Limiting alcohol
• Eating plenty of fibre, fruit, and vegetables
• Limiting red and processed meat
• Maintaining a healthy weight
• Staying physically active
• Taking part in bowel cancer screening

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14. Examination Focus

High-Yield Exam Topics

Sample Viva Questions with Model Answers

Q1: A 55-year-old man has a colonoscopy showing 3 adenomatous polyps, all less than 10mm, tubular, low-grade dysplasia. What is your surveillance plan?

Model Answer: "According to BSG 2020 guidelines, this patient has intermediate-risk findings with 3-4 small adenomas. He should have a surveillance colonoscopy at 3 years. If this is clear, he can have one further colonoscopy at 3 years, then return to population screening.

Key points I would emphasise:

• Low-risk is 1-2 small tubular adenomas with LGD — these patients do NOT need surveillance
• Intermediate-risk includes 3-4 small adenomas OR any adenoma 10-19mm
• High-risk requires ≥5 adenomas, any ≥20mm, or high-grade dysplasia — surveillance at 1 year"

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Q2: Describe the adenoma-carcinoma sequence.

Model Answer: "The adenoma-carcinoma sequence describes the stepwise genetic progression from normal colonic epithelium to invasive carcinoma, first characterised by Fearon and Vogelstein in 1990.

The classical pathway involves sequential mutations:

1. APC mutation (5q21) — initiates adenoma formation by dysregulating the Wnt/β-catenin pathway
2. KRAS mutation (12p12) — promotes adenoma growth through constitutive RAS-MAPK signalling
3. SMAD4/DCC loss (18q21) — loss of TGF-β signalling and cell adhesion
4. TP53 mutation (17p13) — loss of the 'guardian of the genome' allows progression to carcinoma

This process typically takes 10-15 years, providing the rationale for screening intervals.

Importantly, an alternative pathway exists — the serrated pathway, accounting for 15-30% of sporadic CRC, characterised by BRAF mutation, CpG island methylator phenotype, MLH1 hypermethylation, and MSI-high phenotype."

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Q3: A colonoscopy shows > 100 adenomatous polyps in a 22-year-old. What is the diagnosis and management?

Model Answer: "This is familial adenomatous polyposis (FAP) until proven otherwise, caused by germline mutation in the APC gene on chromosome 5q21. It follows autosomal dominant inheritance.

Diagnosis:

• Confirm with genetic testing for APC mutation
• Family history and pedigree analysis
• Screen first-degree relatives

Management:

1. Colorectal: Prophylactic surgery is required, typically by age 25 or when polyp burden becomes unmanageable. Options include:

   • Total proctocolectomy with ileal pouch-anal anastomosis (IPAA) — gold standard
   • Colectomy with ileorectal anastomosis (IRA) — if rectum relatively spared (less than 20 rectal polyps)

2. Upper GI surveillance: Upper GI endoscopy every 1-3 years as 90% develop duodenal adenomas; duodenal cancer risk 5-10%

3. Other surveillance: Thyroid (annual), desmoid screening

4. Family screening: Genetic testing and colonoscopy for at-risk relatives from age 10-12

Without intervention, there is 100% risk of colorectal cancer by age 40-50."

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Q4: How do you risk-stratify a malignant polyp?

Model Answer: "A malignant polyp contains invasive adenocarcinoma (pT1). Risk stratification determines whether polypectomy alone is curative or surgical resection is needed.

Low-risk features (polypectomy may be curative):

• Well or moderately differentiated
• No lymphovascular invasion
• Clear resection margin ≥1mm
• Sm1 invasion (upper 1/3 submucosa) for sessile polyps
• Haggitt level 1-3 for pedunculated polyps
• Low tumour budding

High-risk features (surgical resection recommended):

• Poorly differentiated
• Lymphovascular invasion present
• Margin involved or less than 1mm
• Sm2/Sm3 invasion (sessile)
• Haggitt level 4 (pedunculated)
• High-grade tumour budding

All malignant polyps require MDT discussion. CT staging is performed before surgical decision. The patient's fitness and preferences are considered.

For low-risk lesions, surveillance includes colonoscopy at 3 months to check the polypectomy site, then at 1 year."

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Q5: What are the features of Lynch syndrome and how would you investigate?

Model Answer: "Lynch syndrome, previously called hereditary non-polyposis colorectal cancer (HNPCC), is caused by germline mutations in mismatch repair genes — MLH1, MSH2, MSH6, PMS2, or EPCAM.

Clinical features:

• Autosomal dominant inheritance
• Early-onset colorectal cancer (mean 44 years)
• Right-sided predominance
• MSI-high tumours (poorly differentiated, mucinous, tumour-infiltrating lymphocytes)
• Multiple synchronous/metachronous colorectal cancers
• Extracolonic cancers: endometrial (40-60% risk), ovarian, gastric, urinary tract, small bowel

Investigation:

1. Clinical criteria: Amsterdam II criteria (≥3 relatives, 2 generations, 1 less than 50 years, FAP excluded)
2. Tumour testing:
   • Immunohistochemistry for MMR proteins (loss of expression)
   • Microsatellite instability (MSI) testing
3. Genetic testing: Germline testing for MLH1, MSH2, MSH6, PMS2, EPCAM

Management:

• Colonoscopy every 2 years from age 25 (or 5 years before youngest case)
• Gynaecological surveillance from age 30-35
• Consider prophylactic hysterectomy and BSO after family complete
• Aspirin chemoprevention (CAPP2 trial — 600mg daily for 2 years)
• Immunotherapy for metastatic MSI-high CRC"

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Common Exam Errors

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25. Williams JG, Pullan RD, Hill J, et al. Management of the malignant colorectal polyp: ACPGBI position statement. Colorectal Dis. 2013;15(Suppl 2):1-38. doi:10.1111/codi.12262

26. Ferlitsch M, Moss A, Hassan C, et al. Colorectal polypectomy and endoscopic mucosal resection (EMR): European Society of Gastrointestinal Endoscopy (ESGE) Clinical Guideline. Endoscopy. 2017;49(3):270-297. doi:10.1055/s-0043-102569

27. Burn J, Gerdes AM, Macrae F, et al. Long-term effect of aspirin on cancer risk in carriers of hereditary colorectal cancer: an analysis from the CAPP2 randomised controlled trial. Lancet. 2011;378(9809):2081-2087. doi:10.1016/S0140-6736(11)61049-0

28. Atkin WS, Edwards R, Kralj-Hans I, et al. Once-only flexible sigmoidoscopy screening in prevention of colorectal cancer: a multicentre randomised controlled trial. Lancet. 2010;375(9726):1624-1633. doi:10.1016/S0140-6736(10)60551-X

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17. Additional Clinical Scenarios

Scenario 1: The Screening Colonoscopy

Case: A 62-year-old male has a positive FIT as part of the NHS Bowel Cancer Screening Programme. Colonoscopy reveals a 12mm sessile polyp in the ascending colon and a 6mm pedunculated polyp in the sigmoid. Both are removed.

Histology:

• Ascending colon: Sessile serrated lesion without dysplasia
• Sigmoid: Tubular adenoma with low-grade dysplasia

Questions:

1. How do you risk-stratify this patient?
2. What is the surveillance interval?

Answers:

1. The patient has an SSL less than 10mm without dysplasia (3-year surveillance) AND an adenoma less than 10mm with LGD (no surveillance if only finding). However, when both present, follow the higher-risk lesion.
2. The 12mm SSL (which is ≥10mm) actually requires 1-year surveillance per BSG 2020 guidelines. This takes precedence.

Scenario 2: The Malignant Polyp Dilemma

Case: A 58-year-old female has a 25mm sessile polyp removed by piecemeal EMR from the sigmoid colon. Histology shows moderately differentiated adenocarcinoma invading into Sm2, with no lymphovascular invasion and margins clear by 0.5mm.

Questions:

1. Is this a low-risk or high-risk malignant polyp?
2. What is your management recommendation?

Answers:

1. HIGH-RISK — despite no LVI and moderate differentiation:
   • Sm2 invasion (not Sm1) indicates higher lymph node metastasis risk
   • Margin less than 1mm is concerning
   • Piecemeal resection means margin assessment may be incomplete
2. Management: MDT discussion → recommend surgical resection (sigmoid colectomy) with lymph node clearance. CT staging to exclude distant metastases first.

Scenario 3: The Young Patient with Multiple Polyps

Case: A 28-year-old male presents for colonoscopy due to family history (father died of CRC aged 42). Colonoscopy reveals 8 adenomatous polyps throughout the colon, largest 18mm in the caecum.

Questions:

1. What diagnoses should you consider?
2. What further investigations are needed?

Answers:

1. Consider:
   • Attenuated FAP (10-100 polyps, later onset than classical FAP)
   • MUTYH-associated polyposis (autosomal recessive, 10-100 adenomas)
   • Lynch syndrome (usually few polyps, but strong family history)
2. Further investigations:
   • Genetic testing: APC mutation (FAP), MUTYH (MAP), MMR genes (Lynch)
   • IHC on adenoma tissue if available
   • Upper GI endoscopy (duodenal adenomas in FAP)
   • Family pedigree and genetic counselling
   • Screen siblings and offspring

Scenario 4: The Serrated Lesion Challenge

Case: A 55-year-old female has a colonoscopy for iron deficiency anaemia. In the proximal transverse colon, a 20mm flat lesion is identified, pale with indistinct margins, covered in adherent mucus. It is removed by piecemeal EMR.

Histology: Sessile serrated lesion with low-grade dysplasia.

Questions:

1. Why are these lesions clinically important?
2. What is the surveillance plan?

Answers:

1. SSLs with dysplasia are important because:
   • They follow the serrated pathway to CRC (BRAF → MLH1 methylation → MSI-high)
   • May have accelerated progression to cancer
   • Often flat and pale — easily missed (high miss rate)
   • Account for many "interval cancers"
2. Surveillance plan:
   • Site check at 2-6 months (piecemeal resection of large lesion)
   • If clear, 1-year surveillance (SSL with dysplasia = high-risk)
   • High-quality colonoscopy with chromoendoscopy recommended

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18. Quick Reference Summary Cards

BSG 2020 Surveillance Quick Reference

Polyposis Syndromes Quick Reference

Malignant Polyp Risk Stratification Quick Reference

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Last Reviewed: 2025-01-09 | MedVellum Editorial Team

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Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists and refer to current national guidelines.