Resection and Prognosis of Adenomatous Polyps

ad

Endoscopic polypectomy reduces the subsequent incidence and mortality of colorectal cancer.

Although patients with adenomatous polyps are likely asymptomatic, they may have positive stool occult or evident hematochezia.  The lifetime recurrent incidence of adenomas in patients who had polypectomy is 30 to 50%. Less than 5% of all adenomas likely become cancerous.  The likelihood of an adenoma becoming cancerous depends on two factors that are the size of the polyp and the grade of dysplasia.  For polyps less than 1 cm, the risk of becoming cancerous is 1 to 3%; for those between 1 and 2 cm, the risk is 10%; and for those greater than 2 cm, the risk is 40% or greater.  Although all adenomatous polyps are dysplastic to some extent, they can be categorized as low and high dysplastic grades that indicate the risk of becoming cancerous.  If adenomatous polyps contain high-grade dysplasia, the risk of becoming cancerous rises to as high as 27%. 

f:id:tpspi:20161103141830j:plain

credit:  snare polypectomy  Olympus

 

Diagnosis

Adenomatous polyps that occur in the colon and rectum can be accurately diagnosed by endoscopy.  Since colonoscopy is highly accurate and can immediately cut most polyps, it is the most preferred diagnosing method for adenomas. 

Resection

During endoscopy, adenomatous polyps can be removed by an endoscopic snare.  Endoscopy is strongly recommended because scientific evidence shows that endoscopic polypectomy reduces the subsequent incidence and mortality of colorectal cancer.  Pedunculated adenomas are generally removed by an endoscopic snare.  The removed adenomas are pathologically analyzed to examine whether it became cancerous.  Sessile polyps may be cut piecemeal by an endoscopic snare.  Large adenomas unsuitable for endoscopic resection are surgically removed.  The removed polyp must be histologically examined to reveal whether it is cancerous.  If the polyp is cancerous, its histologic malignant grade, vascular and lymphatic involvement, and the margin of cancer need to be evaluated.  If the removed polyp indicates poorly differentiated histology, vascular invasion, lymphatic invasion, or incomplete endoscopic resection, immediate surgical resection is required.  Even if a pedunculated polyp is cancerous and confined to the submucosa, unless it has unfavorable histologic features, it can be removed endoscopically rather than surgically. 

 

Prognosis

Patients who have experienced polypectomy have an increased risk for recurrence of adenoma and development of carcinoma.  This risk depends on the size, histology, number of adenomas, and intervals for treatment.  Although the risk of patients with only one or two small tubular adenomas is low, they are recommended to have colonoscopy within 5 years.  Patients with three or more adenomas, those with an adenoma larger than 1 cm, or those with villous or high grade dysplastic adenomas need to have colonoscopy within 3 years.  Patients with more than ten adenomas need to have colonoscopy within 3 years.  Patients who have experienced polypectomy for an adenoma larger than 2 cm or an adenoma that had been removed piecemeal need to have colonoscopy within 6 months to confirm the completeness of the resection.