Colorectal Polyps : Types, Neoplastic Polyps

Colorectal Polyps

A polyp is a protrusion of tissue into the lumen above the surrounding intestine mucosa. Colorectal polyps are asymptomatic but large size polyps may bleed or cause obstructive symptoms. Some colorectal polyps, such as adenomatous polyps, are precursors of cancers. 

Types Of Colorectal Polyps

The types of colorectal polyps can be classified based on endoscopic appearance: pedunculated, which has a stalk, and sessile, which means flat. The types can also be classified based on histological appearance: adenomas, hamartomas, inflammatory, and serrated.  Let us read about some types briefly: 

1. Neoplastic Polyps: Neoplastic polyps are at risk of developing colorectal cancer. Therefore, they should be removed to reduce the risk. 
2. Non - Neoplastic polyps: Non-neoplastic polyps include hyperplastic, inflammatory, and hamartomatous polyps. 
3. Hyperplastic Polyps: The most common non-neoplastic polyp is hyperplastic polyp. These are usually small lesions with a size less than 5mm. They consist of elongated colonic crypts with a papillary configuration of epithelial cells. There is no atypia and no malignant potential. 
4. Inflammatory Polyp: An inflammatory polyp, also known as a pseudopolyp, is formed in the areas of regeneration after ulceration. The new mucosa forms an irregular polypoid configuration. It is seen in inflammatory bowel diseases such as ulcerative colitis and Crohn's disease, most commonly in ulcerative colitis. It does not have malignant potential.    

5. Hamartomatous Polyps: Hamartomatous polyps are commonly related to genetic syndromes such as Peutz-Jeghers syndrome, juvenile polyposis syndrome with multiple hamartomatous polyps, and Pten hamartoma syndrome.  There is no potential for malignancy. The removal of hamartomatous polyp should be considered in case of obstruction and bleeding. 

6. Serrated Polyps: There are three types of serrated polyps: hyperplastic serrated polyps, sessile serrated polyps, and traditional serrated polyps. The sessile serrated polyp and traditional serrated polyp have features of a combination of adenomatous and hyperplastic polyps. They have colonic crypts with saw-tooth serrated configuration and nuclear atypia. There is an increased risk of colorectal cancer in sessile serrated and traditional serrated polyps due to the presence of an adenomatous component. The development of colorectal cancer follows a serrated neoplasia pathway. The serrated polyps should be removed and followed up endoscopically.  

Let's now discuss some of the common polyps that we study in detail. These types are very commonly seen in doctors' daily lives.

Neoplastic Polyps

Neoplastic polyps are known as adenomas. All adenomas have malignant potential. Therefore, all the adenomas should be excised. There are three types of neoplastic polyps: tubular, villous, and tubulovillous. 

Tubular

The most common type is tubular, comprising 65-80% of neoplastic polyps. On histology, branched tubular glands are present, usually pedunculated. If the size of the tubular polyp is less than 1 cm, there is a 5% risk of carcinoma. 

Villous type

5-10% of neoplastic polyps are villous type. It is the most malignant type. It looks like villi, i.e., finger-like projections of surface epithelium. These are sessile. There is a 50 % chance of carcinoma if the size is over 2cm. 

Tubulovillous type

The tubulovillous type is 10-25% of neoplastic polyps. It has elements of both.   

The Risk of malignancy depends on size, gross shape, histologic type and grade of dysplasia. 

Advanced adenoma

An advanced adenoma is defined as one that is at least 1cm in size, has high-grade dysplasia, and has tubulovillous or villous histology. Patients with advanced adenomas are at a significantly increased risk of colorectal cancer. 

Management Of Avanced Adenoma

An adenomatous polyps should be excised as these have malignant potential.  The pedunculated polyps can be removed using cold and hot snare polypectomy. The sessile polyps are elevated by saline injection followed by excision.

Sessile polyp with a central depression 

A sessile polyp with central depression has a non-lifting sign that cannot be elevated with saline injection. These polyps have an increased risk of perforation with endoscopic removal and a higher risk of harboring neoplasia. This is treated with removal by segmental colectomy.  The Kikuchi classification is used for the classification of sessile polyps. 

• SM1 is directly involved in the upper third of the submucosa. 
• SM2 is a direct invasion of the middle third of the submucosa.
•  SM3 is a direct invasion into the lower third of the submucosa.  

Malignant Polyps

Malignant polyps are associated with the focus of carcinoma that invades the muscularis mucosa. If the carcinoma does not invade the muscularis mucosa, it is called carcinoma in situ. There is no metastatic risk in such patients. In the invasion of the muscularis mucosa, there is an increased risk of local recurrence and lymph node metastasis. The important risk factor is the depth of penetration. Haggit's classification defines it as malignant polyps. Haggit's classification for pedunculated carcinoma is as follows: 

• Level 0 is carcinoma in situ. The carcinoma is limited to mucosa. 
• In level 1, the carcinoma invades the submucosa but is limited to the head.
• In level 2, the carcinoma invades the neck i.e., the junction of the head and stalk. 
• Level 3 is carcinoma invading any part of the stalk.  
• In level 4, the colon's submucosa is involved. The carcinoma invades the submucosa of the colon wall below the level of the stalk but above the muscularis propia. 

Also Read: Anatomy of Spleen : Comprehensive Guide

Management of malignant polyps 

The malignant polyps are referred for completion of colectomy.  A completion colectomy is referred to patients with pedunculated Haggits level 4, sessile Kikuchi level SM2, SM3, histologically poorly differentiated polyps, polyps with lymphovascular invasion, and incomplete removal or close resection margins. These patients have a risk of residual cancer or lymph node metastasis of more than 10%. 

Also Read: Biliary Tree Pathophysiology & Investigations

Post Polypectomy Surveillance

The detection of adenoma by colonoscopy is a risk factor for the future development of additional polyps. Therefore, post-polypectomy surveillance is needed. The current recommendations for repeat colonoscopy following endoscopic removal of polyps are as follows:

Also read: High-Yield GIT, Hepatobiliary and Pancreatic Surgery Questions

Hope you found this blog helpful for your GIT, Hepatobiliary and Pancreatic Surgery preparation. For more informative and interesting posts like these, keep reading PrepLadder’s blogs.