• See Hereditary cancer syndromes
• Neoplastic
  • Sessile serrated polyp
  • Adenomatous (villous > tubular)
• Nonneoplastic
  • Hyperplastic
  • Inflammatory
  • Hamartomatous

Adenomatous polyps

• High malignant potential
  • Tubular adenoma: < 5%
  • Tubulovillous adenoma: ∼ 20%
  • Villous adenoma: ∼ 50%

Mnemonic

Villous adenomas are villains because they have the highest malignant potential.

Hyperplastic polyps

• Most common type of nonneoplastic polyp among those with low malignant potential
• Histology: hyperplasia of normal cellular components with a sawtooth/serrated pattern of crypt epithelium
  • No dysplasia, see Cellular adaptations

Hamartomatous polyposis syndromes

Peutz-Jeghers syndrome (PJS)

• Inheritance: autosomal dominant
• Intestinal manifestations
  • Large polyps can manifest with abdominal pain, GI bleeding, or intestinal obstruction.
  • Lifetime colorectal cancer risk: ∼ 40% (onset typically occurs at ∼ 45 years of age) and increased risk of other GI malignancies (e.g., small bowel, pancreatic, stomach cancer)
• Extraintestinal manifestations
  • Mucocutaneous hyperpigmented macules (i.e., lentigines) on the lips, buccal mucosa, genitals, palms, soles (seen in 95% of patients)
    • Due to affecting melanocytes, leading to the overproduction of melanin and the development of hyperpigmented macules.
  • Increased risk of non-GI tract cancers (e.g., breast cancer, ovarian cancer)
• Endoscopy and histology: hamartomatous PJS polyps throughout the GI tract
  • PJS polyps are hamartomatous, with mucin-filled cystic spaces and significant smooth muscle proliferation.