- 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 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. |