Makindo Medical Notes

Normal Epithelium → Dysplastic Epithelium → Adenoma → Adenocarcinoma

About

• A protuberance of colorectal mucosa into the lumen.
• Importance lies in identifying polyps with malignant potential.

Neoplastic Polyps

• These are primarily adenomas that can develop into adenocarcinomas.
• At autopsy, around one-third of people have an adenomatous polyp.
• Most occur beyond the splenic flexure; the concern is the adenoma-carcinoma sequence.

Adenomatous Polyps: Malignancy Risk Factors

• Degree of dysplasia: Increased mitotic figures, pleomorphism of nuclei, loss of polarity, and layering.
• Size of polyps: Larger polyps (e.g., >2 cm) have higher risk.
• Villous adenomas: Highest risk of malignancy.
• Tubulovillous or Tubular adenomas: Lower risk but still significant.
• Carcinoma in situ: Severe dysplasia confined to the mucosa.
• Malignant transformation: Occurs when there is invasion of the muscularis mucosa.
• Adenomatous polyps should be removed when detected, followed by complete colonoscopy to check for additional polyps. Metaplastic polyps do not require follow-up.

Genetic Syndromes with Adenomatous Polyps

• Familial Adenomatous Polyposis (FAP): Autosomal dominant mutation in APC gene leading to numerous colorectal polyps.
• Turcot's Syndrome: FAP associated with glioblastomas or medulloblastomas.
• Gardner's Syndrome: FAP with additional osteomas, soft tissue tumors, and sebaceous cysts.

Non-Neoplastic Polyps: No Malignant Potential

• Metaplastic Polyps (Hyperplastic): Commonly found in the rectum, small (2-5 mm), and flat. They do not become dysplastic or malignant.
• Inflammatory Pseudopolyps: Seen in inflammatory bowel diseases such as ulcerative colitis (UC) and Crohn's disease (CD).
• Hamartomatous Polyps: Includes polyps in Peutz-Jegher's syndrome and Juvenile polyps, which are typically found in children under 10, often in the rectum, and may cause bleeding or prolapse through the anus. They are easily resected.

Genetic Syndromes with Hamartomatous Polyps

• Peutz-Jegher's Syndrome: Autosomal dominant with characteristic mucocutaneous pigmentation of lips and gums. Involves small bowel and colonic polyps, with potential complications like childhood intussusception or bleeding.
• Cronkhite-Canada Syndrome: Presents with alopecia, nail atrophy, skin hyperpigmentation, and watery diarrhoea.