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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

Endoscopic appearance of a pedunculated benign adenomatous polyp

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

Circumoral pigmentation of Peutz-Jegher's syndrome

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  

Histology of an adenomatous polyp

  • 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 20ís
  • Untreated progresses to cancer by 30ís
  • Screening Ė 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 = Gardenerís 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

Colonic surface appearances of familial adenomatous polyposis

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 years
  • Recommend to start colonoscopic screening starting 5 years before youngest affected relative.

Bibliography

Campbell W J,  Spence R A J,  Parks T G.   Familial adenomatous polyposis.  Br J Surg 1994; 81: 1722 - 33.

 

 
 

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