Polyps, Intestinal

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DESCRIPTION

  • Intestinal polyps are abnormal tissue growths protruding from the intestinal mucosa into the lumen.
    • Most common in children are solitary juvenile polyps, but these may also be multiple in number.
    • May be associated with various polyposis syndromes
  • Classified by gross appearance
    • Pedunculated: mushroom-like and attached to mucosa with a narrow stalk
    • Sessile: height >1/2 base diameter
    • Flat: height <1/2 base diameter
  • Types of polyps:
    • Hamartomas
    • Adenomatous
  • Hamartomatous polyps
    • Juvenile polyps: usually a solitary polyp
    • Juvenile polyposis syndrome (JPS): >5 juvenile polyps in the colon, any number of polyps involving both upper and lower gastrointestinal (GI) tract, or any number of juvenile polyps with a positive family history of JPS
      • Juvenile polyposis of infancy
      • Juvenile polyposis coli (colonic involvement only)
      • Generalized juvenile polyposis (small bowel and colonic involvement)
    • Peutz-Jeghers syndrome
    • PTEN hamartoma tumor syndrome
      • Cowden syndrome
      • Bannayan-Riley-Ruvalcaba syndrome (BRRS)
  • Adenomatous polyps
    • Familial adenomatous polyposis (FAP) (a.k.a. Gardner syndrome)
      • Profuse (severe), classic, and attenuated forms
      • Gardner syndrome (colonic polyps with osteomas and epidermal inclusion cysts)
    • Constitutional mismatch repair deficiency (CMMRD)
      • Biallelic loss of mismatch repair gene (e.g., MSH2, MLH1, MSH6, PMS2)
      • Early onset of polyposis, as well as high risk of pediatric cancer, especially brain tumors and lymphomas
    • Turcot syndrome (colonic polyps with brain tumors, variant of FAP, CMMRD, or Lynch syndrome)
  • Other polyposis syndromes, adult onset
    • MUTYH-associated polyposis syndrome
    • Serrated polyposis syndrome

EPIDEMIOLOGY

  • Juvenile polyps are the most common childhood polyps:
    • Account for >90% of polyps seen in children
    • 1–2% of asymptomatic children are estimated to have juvenile polyps.
    • Typically present between 2 and 5 years of age
    • Twice as common in boys than girls
    • >5 juvenile polyps should raise clinical suspicion for JPS.
  • Adenomatous polyps in FAP may present in early childhood or adolescence with an average age of onset of 16 years.

Prevalence

  • JPS: 1 in 100,000 to 1 in 160,000
  • Peutz-Jeghers syndrome: 1 in 25,000 to 1 in 300,000
  • FAP: 1 in 5,000 to 1 in 17,000

RISK FACTORS

Family history of polyposis syndrome

Genetics

Different genes and inheritance patterns with various polyposis syndromes:

  • JPS
    • Autosomal dominant
    • Mutations in SMAD4 and BMPR1A genes, involved in transforming growth factor-β (TGF-β) signal transduction
    • SMAD4 mutation also associated with hereditary hemorrhagic telangiectasia (HHT) and requires further screening for arteriovenous malformations.
    • If no mutation detected, overall polyp burden and cancer risk may be lower.
  • Peutz-Jeghers syndrome
    • Autosomal dominant
    • Mutations in STK11/LKB1 tumor suppressor gene are associated.
  • PTEN hamartoma tumor syndrome
    • Autosomal dominant
    • Associated with mutations in PTEN gene
  • FAP
    • Autosomal dominant
    • Mutation in adenomatous polyposis coli (APC) tumor suppressor gene
  • CMMRD
    • Autosomal recessive
    • Mutation in mismatch repair genes (e.g., MSH2, MLH1, MSH6, PMS2)
    • Parents with autosomal dominant Lynch syndrome

PATHOPHYSIOLOGY

Mutations in tumor suppressor genes likely lead to dysregulation of cell proliferation and apoptosis in polyposis syndromes.

COMMONLY ASSOCIATED CONDITIONS

  • JPS and PTEN hamartoma tumor syndrome all have juvenile polyps as part of their manifestations.
    • PTEN hamartoma tumor syndrome is associated with colonic and gastric polyps with extraintestinal symptoms including mucocutaneous lesions, thyroid adenomas and goiter, fibroadenomas and fibrocystic disease of the breast, uterine leiomyomas, macrocephaly, and autism.
  • Peutz-Jeghers syndrome is characterized by multiple GI pedunculated hamartomatous polyps.
  • FAP is characterized by multiple adenomatous polyps.

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