Benign colonic polyps

• A polyp is a pedunculated lesion
• Not all polyps are tumours
• Not all polypoid tumours are benign
• Not all benign tumours are polypoid

Classification of large bowel polyps

• Epithelial
  • Adenomas - tubular, villous, tubulovillous
  • Metaplastic polyps
• Mesodermal
  • Lipoma
  • Leiomyoma
  • Haemangioma
• Hamartoma
  • Juvenile polyps
  • Peutz-Jeghers syndrome

Juvenile polyps

• Commonest form of polyp in children
• Can occur throughout large bowel but are most common in the rectum
• Usually present before 12 years
• Present with Prolapsing lump or rectal bleeding
• Not pre-malignant
• Treated by local endoscopic resection

Peutz-Jeghers syndrome

• Rare familial disorder
• Circumoral pigmentation and intestinal polyps
• Polyps found throughout gut but most common in the small intestine
• Presents in childhood with bleeding, anaemia or intussusception
• Polyps can become malignant

Metaplastic polyps

• Small plaques approximately 2 mm in diameter
• Pathogenesis unknown
• Not pre-malignant

Adenomas

• Benign epithelial neoplasm
• They are pre-malignant
• Risk of malignancy increases with size
• Malignancy more common in villous rather than tubular lesions

• Most adenomas are asymptomatic
• 10% of population over 45 years have adenomatous polyps
• If do become symptomatic usually present with bleeding, mucous discharge or prolapse
• Villous adenomas may produce hypokalaemia but this is rare
• Diagnosis is often by sigmoidoscopy or colonoscopy
• Full colonoscopy essential to exclude other lesions
• Treatment is by transanal excision or colonoscopic snaring
• Patients require regular colonoscopic surveillance

Familial adenomatous polyposis

• Aetiological factor in 1% of colorectal cancers
• Its is an autosomal dominant
• Due to mutation on long arm of chromosome 5
• Mutation induces proliferation of mucosa throughout GI tract
• Develop colonic polyps in teens or early 20’s
• Untreated progresses to cancer by 30’s
• Screening – by rigid or flexible sigmoidoscopy
• Safe alternative to colonoscopy as rectal sparing rarely seen
• Start late teens and continue until 40 yrs and polyp free.
• Extra-colonic manifestations:
  • Osteomas. epidermoid cysts = Gardener’s Syndrome
  • Gastroduodenal polyps
  • Desmoid tumours
  • Congenital hypertrophy of retinal pigmented epithelium
• Surgical options:
  • Panproctocolectomy and ileostomy
  • Restorative panproctocolectomy
  • Subtotal colectomy and ileorectal anastomosis
  • NB will require surveillance of rectal stump

Hereditary non-polyposis colorectal cancer syndrome

• Accounts for 5-10% of colorectal cancers
• Results in mainly right sided cancers
• Increased risk of other gastrointestinal, urological and gynaecological malignancy
• Diagnosed by having 3 affected relatives, in 2 generations and one patient <50>
• Recommend to start colonoscopic screening starting 5 years before youngest affected relative.

Category: Pathology Notes