COLORECTAL POLYPSCOLORECTAL POLYPS

PROF. DR. TURGUT IPEK

POLYPSPOLYPS

HamartomaHamartomaPeutz-Jeghers Syndrome: The combination of hamartomatous polyps of smooth muscles andsubcutaneous pigmentation was first described in 1896 by Hutchinson. The existence of familialhamartomatous polyps was originally described byPeutz and later in 1949 in follow-up article byJeghers.

The syndrome consist of pigmentation, produced by melanin in themucocutaneous areas, and of hamartomas of intestinal smooth musclethroughout the gastrointestinal tract.

This is autosomal dominant syndrome andcarries with it a well-documented risk of cancer in the breast, cervix, ovary, fallopian tubes, thyroid, lung, skin(basalcell) gallblader, pancreas, testicle, and bile duct. An overall risk of 2 to 13 percent fordeveloping intestinal cancer arising in thestomach, small intestine, and colon has been documented in these patients.

Symptoms of the hamartomas includebleeding or intestinal obstructionsecondary to intussusception. Treatmentincludes removing and polyp that is greater than 1.5 cm, even if asymptomatic.

JuvenileJuvenile PolyposisPolyposisJuvenile polyposis was first described byVerse in 1908. The familial inheritance of these polyps was reported by Veale at St. Mark’s in 1966. Juvenile polyps occur as cystic dilations of glandular structureswithin the fibroblastic stroma of the laminapropria.

Juvenile polyps usually cause symptomsof gastrointestinal bleeding or obstructiondue to intususception, with the polyp of thelead point. The most common cause of gastrointestinal bleeding in a child is a juvenile polyp.

Multiple polyposis coli (diffuse juvenilepolyps) is an autosomal dominant withhigh penetrance which carries an increased risk of cancer in the GI tract andin other nongastrointestinal tissues.

Diffuse juvenile polyposis occurs in lessthan 1 percent of patients with juvenilepolyps and may carry an even higher risk of cancer when there are mixed orheterogeneous types of polyps present. The malignant potential has beenestimated at approximately 10 percent in patients with the multiple polyposis colitype of juvenile polyposis.

HyperplasticHyperplastic PolypsPolypsHyperplastic polyps are common in thecolon. They have been estimated to be ten times more common than adenomas. Their typical histologic findings consist of epithelial dysmaturation and hyperplasia.

They are usually less than 5 mm in diameter and show a thickened mucosawithout atypia. Hyperplastic polyps can be biopsied, destroyed, or removed duringcolonoscopy.

OtherOther LesionsLesionsThere are several other less well-known andrare hamartomatous syndromes.Cowden’s syndrome is an autosomal dominant defect which includes hamartomas of all threeembryonal cell layers. Tricholemmomas, breastcancer, thyroid disease, and gastrointestinalpolyps with occasional gastrointestinal cancersare typical of the syndrome. Treatment is basedon symptoms. Polyps should be removed, andthe patient screened for other cancers.

Cronkhite-Canada syndrome is typified byjuvenile polyps in a nonfamilial setting withother epidermal changes but no evidenceof malignancies. The polyps should be removed only if they cause symptoms.

The Ruvalcaba-Myhre-Smith syndromeincludes developmental abnormalities, microcephaly, and juvenile polyps. It is a very rare syndrome that occurs in males, and to this date, no cancers have beendocumented.

AdenomaAdenoma

PathologyPathologyThe adenoma, or adenomatous polyp, of the colon or rectum is a benign neoplasm. Polyps can exist in a pedunculated (with a stalk), sessile (flat), or semisessile (raised) form.

Polyps are classified as tubular adenoma, tubulovillous adenoma, villous adenoma depending on the predominant pattern. Ingeneral, 65 to 80 percent of alladenomatous polps removed are tubularadenomas, 10 to 25 percent aretubulovillous and only 5 to 10 percent arepure villous adenomas. Tubular adenomasare usually pedunculated and villousadenomas are usually sessile.

The term severe atypia is now acceptedfor the finding of a malignancy in theepithelium of a polyp that has not invadedthorough the muscularis mucosae of thebowel. Such lesions were previouslyreferred to as “carcinoma in situ”.

PoypPoyp--CancerCancer SequenceSequenceIt is generally accepted that a benign adenoma

has been precursor to acolorectel cancer in the majority of cases.

The evidence for the existence of an adenoma-carcinoma sequence includes following:1. Polpectomy has been shown to decrease the incidence

of cancer. Patients with small adenomas have a 2.3 times increased risk of cancer after polypectomies as compared to an eightfold increase in the risk of cancerin patients who do not undergo polypectomy.

2. Colonic adenomas are more frequentlyobserved in patients with cancer. Nearly30 percent of all patients with a colorectal cancer will also havesynchronous poly.

3. Larger adenomas are more often found to containcancer and severe dysplasia than smaller polyps. Sixtypercent of adenomas greater than 2 cm are villousadenomas. Villous adenomas have 40 percent risk of containing a cancer as compared with a 22 percentrisk of cancer in tubulovillous adenomas and a 5 percent risk of cancer in tubular adenomas; however, the size of the polyp seem to be more important thanthe histologic features. The risk of a cancer in a villousadenoma, tubulovillous adenoma, or tubular adenoma greater than 2 cm is 53 percent, 46 percent, and 35 percent, respectively.

4. Severe dysplasia has been shown toprogress to cancer in polyps. Thedifferentiation between carcinoma in situand anvasive cancer relies on the depthof invasion of the dysplastic area. Invasion beneath the muscularismucusae defines invasiveadenocarcinoma in a polyp, because thecancer cells at this depth have access tothe vascular and lymphatic systems.

5. Residual adenomatous tissue is found in the majority of invasive cancers. This is presumptive evidence that the cancerhas arisen within the polyp and has progressed to replace the majority of thepolyp.

6. Patients with familial adenomatouspolyposis(>100 polyps) develop cancer100 percent of the time if the colon is not removed. The adenomas of FAP arehistologically the same as sporadicadenomas.

7. There is a high prevalence of adenomasin populations with a high rate of cancer. This seems to indicate that the polyp is a precursor or a necessary factor in thedevelopment of cancer.

8. It has been shown that the presence of an adenoma places a patient at a lifetimerisk for the development of cancer.

9. The peak incidence for the developmentof cancer is at sixty years of age. Thiswould indicate that there is a ten-yeartime span for the conversion of theadenomatous polyps to cancer. Investigatigators at Mayo Clinicdocumented that a polyp greater than 1 cm has a cancer risk of 2.5 percent in 5 years, 8 percent in 10 years, and 24 percent in 20 years.

TreatmentTreatment

PedunculatedPedunculated PolypsPolypsPedunculated polyps have a stalk which is usually less than 1.5 cm in diameter. Colonoscopic polypectomy is the besttreatment for the most pedunculatedpolyps.

SemisessileSemisessile PolypsPolypsSemisessile polyps have a broad pedicle, greater than 1.5 cm. These polyps can usually be removed in piecemeal fashion ifthey do not have a malignant appearance.

SessileSessile PolypsPolypsSessile polyps greater than 2 cm can usually be removed in piecemeal fashionalso.

The complications of colonoscopicpolypectomy include perforation, eitherimmediate or delayed, due to a cauteryburn or snare of full-thickness bowel wallduring removal of a semisessile or sessilepolyp.

ColectomyColectomyCancer in the head of a polyp may be treated by colonoscopic polypectomy. However, one must be prepared toperform colectomy when the cancer withinthe head of the polyp has unfavorablefeatures.

The risk of local recurrence is at least 10 percent, and the risk of spread of cancerto lymp npdes is approximately 10 percentin these patients. Therefore, even ifcompletely excised, the sessile polyp withan invasive carcinoma requires colectomyfor complete cure.

Villous Adenoma of the Rectum:

Villous adenomas of the rectum aretypically flat, velvety, and soft sessilepolyps within the rectum. Theyoccasionally present with watery diarrheaand hypokalemia. The finding of a large(greater than 4 cm) villous adenoma in therectum, with areas of induration, indicatesa very high risk for cancer (90 percent).

Transrectal ultrasound of the villous lesionis helpful to determine the thickness of thelesion. Ultrasound, however, is unable todistinguish between carcinoma in situ andinvasive cancer. If cancer is present, thepatient should ne treated with appropriateresection. The transanal excision shouldinclude adequate peripheral margins forcomplete cure if cancer is not present.

PolyposisPolyposis SyndromesSyndromes

FamilialFamilial AdenomatousAdenomatous PolyposisPolyposisLemuel Herrera discovered the underlyinggenetic abnormality, at APC gene, in 1986. The APC gene is located in the longarm of chromosome 5, precisely betweenD5S49 and D5S58.

ClinicalClinical presentationpresentationMost FAP patients will die of colorectalcarcinoma before the age of 40 if leftuntreated.In the typical family with FAP, 80% of individuals with APC gene mutation willdevelop polyps before the age of 20. Mostpolyps measure less than 5 to 10 mm in size.

Polyps larger than 2 to 3 cm usuallycontain foci of cancer.Patients with more than 1000 polyps had a 2.3 times greater risk of cancer than thosewith fewer than 1000 polyps, that theincidence of synchronous cancerscorrelated with polyp count, and that foreach 10-year age increase, ther wa a 2.4-fold increase in cancer risk.

If an FAP patient becomes symptomatic, it usually is in the form of diarrhea. Rectalbleeding is usually a sign of cancer ratherthan of polyps.Other manifestations of FAP arecongenital hypertropht of the retinalepithelium, osteomas, and fibromatosis.

The association of FAP with brain tumorsis known as Turcot’s syndrome. The tumorfound in these patients includeglioblastomas and medulloblastomas. They usually present around the age of puberty.

SurgicalSurgical optionoptionThere is no doubt that patients who arediagnosed with the APC gene mutationmust have their colon removed. The onlypoints of controversy are the need forremoval of the rectum and the timing of the surgery.

ReferencesKodner IJ, Fry RD, Fleshman JW, Birnbaum EH Colon,Rectum,and Anus. Principles of SurgeryEd. Schwartz SI McGraw Hill 1994, 1191-1306.Corman ML Colon and Rectal Surgery. Lippincott Williams and Wilkins Philadelphia2005, 701-766.Rolandelli RH, Rosly JJ Colon and Rectum. Sabiston Textbook of Surgery Ed. TownsendCM, WB Saunders Company Pennsylvania, 2001, 929-973.