Colon
Polyps
Polyp overview
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Table of Contents
Definition / general | Essential features | ICD coding | Epidemiology | Pathophysiology | Etiology | Clinical features | Diagnosis | Laboratory | Radiology description | Prognostic factors | Treatment | Gross description | Microscopic (histologic) descriptionCite this page: Erem A, Van Treeck B, Hartley C. Polyp overview. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/colontumorpolypgeneral.html. Accessed April 23rd, 2024.
Definition / general
- A polyp is an exophytic or sessile lesion distinct from the mucosal surface and may be neoplastic or nonneoplastic
Essential features
- > 95% of colorectal adenocarcinoma arises from polyps
- Usually asymptomatic
ICD coding
- Benign adenomatous:
- D12.0 - benign neoplasm of cecum
- D12.2 - benign neoplasm of ascending colon
- D12.3 - benign neoplasm of transverse colon
- D12.4 - benign neoplasm of descending colon
- D12.5 - benign neoplasm of sigmoid colon
- D12.6 - benign neoplasm of colon, unspecified; or polyposis of colon
- D12.7 - benign neoplasm of rectosigmoid junction
- D12.8 - benign neoplasm of rectum
- Inflammatory:
- K51.40 - inflammatory polyps of colon without complications
- K51.411 - inflammatory polyps of colon with rectal bleeding
- K51.412 - inflammatory polyps of colon with intestinal obstruction
- K51.413 - inflammatory polyps of colon with fistula
- K51.414 - inflammatory polyps of colon with abscess
- K51.418 - inflammatory polyps of colon with other complication
- Other:
Epidemiology
- Varies by type of polyp
- For more information on epidemiology of colon polyps, please refer to the individual chapters pertaining to each type of polyp in Pathology Outlines
Pathophysiology
- Etiology of colonic polyps varies from neoplastic to nonneoplastic and can either arise sporadically or in syndromic context
Etiology
- Examples of risk factors for adenomatous polyps:
- Smoking
- Twofold - threefold increased risk of all polyp types in smokers (Best Pract Res Clin Gastroenterol 2017;31:419)
- Serrated polyps: relative risk is 2.47 (Gastroenterology 2017;152:92)
- Increased adenoma risk in distal colon and rectum (Am J Epidemiol 2013;177:625)
- Women who use estrogen hormone replacement therapy: increased serrated polyps (Am J Epidemiol 2013;177:625)
- Alcohol (Gastroenterology 2017;152:92)
- Serrated polyps: relative risk is 1.33 (Gastroenterology 2017;152:92)
- Diet high in fat or meat (Gastroenterology 2017;152:92)
- BMI
- Serrated polyps: relative risk of high BMI is 1.4 (Gastroenterology 2017;152:92)
- BMI ≥ 30: increased distal colon and rectal serrated polyps (Am J Epidemiol 2013;177:625 Gastroenterology 2017;152:92)
- Decreased risk:
- NSAIDs, aspirin, diet high in folate, calcium or fiber (Gastroenterology 2017;152:92)
- Smoking
Clinical features
- Clinical impression correlates poorly with neoplasia (J Gastroenterol Hepatol 2006;21:563, World J Gastroenterol 2018;24:905)
Diagnosis
- Colonoscopy with polypectomy and histopathological evaluation is the gold standard
- 80% are diminutive polyps (1 - 5 mm) (Gastroenterology 2017;152:1821, Curr Opin Gastroenterol 2016;32:38)
- "Resect and discard" strategy: real time optical diagnosis without histopathological evaluation for diminutive colonic polyps (1 - 5 mm) (World J Gastroenterol 2016;22:6049)
- Diminutive polyps present 0 - 0.6% risk of cancer (World J Gastroenterol 2016;22:6049)
- Recommended only for expert centers (Curr Opin Gastroenterol 2016;32:38, Ann Gastroenterol 2017;30:592)
- “Diagnose and leave behind” strategy: real time optical diagnosis without polypectomy for hyperplastic polyps located in the rectosigmoid, as they harbor a cancer risk even lower than diminutive polyps (World J Gastroenterol 2016;22:6049, Curr Opin Gastroenterol 2016;32:38)
- Resection is not mandatory for endoscopists with high degree of expertise and use of novel real time optical tools (narrowband imaging [NBI], flexible spectral imaging color enhancement [FICE] and i-SCAN digital contrast [i-SCAN]) (Endoscopy 2017;49:270)
- High confidence required for diagnosis of hyperplastic polyp without tissue sampling (Curr Opin Gastroenterol 2016;32:38)
- Cold forceps biopsy, hot forceps biopsy (HFB), cold snare polypectomy, hot snare polypectomy for pedunculated polyps
- Discussed in the Treatment section
- Advanced endoscopic imaging:
- Goal is to avoid over or undertreatment (Bianco: Colon Polypectomy - Current Techniques and Novel Perspectives, 1st edition, 2018)
- Chromoendoscopy uses contrast dyes (Gastrointest Endosc 2018;88:674)
- Narrow band imaging does not use dyes to enhance mucosal surface (GE Port J Gastroenterol 2018;26:40, Gut 2014;63:785, Dig Liver Dis 2014;46:803 Am J Gastroenterol 2014;109:855)
- Examples of chromoendoscopy include:
- Fujinon intelligent chromoendoscopy (World J Clin Oncol 2017;8:168)
- i-scan (PLoS One 2018;13:e0197520, Eur J Gastroenterol Hepatol 2017;29:1309, PLoS One 2015;10:e0126237)
- Others: high definition white light colonoscopy, cap assisted colonoscopy, RetroView, Full Spectrum Endoscopy Colonoscope, Third Eye Retroscope, Third Eye Panoramic, NaviAid G-EYE balloon colonoscope, EndoRings, Endocuff, magnification endoscopy, virtual chromoendoscopy, flexible spectral imaging color enhancement (FICE), STORZ, autofluorescence imaging, confocal laser endomicroscopy, endocytoscopy, optical coherence tomography, spectroscopy, colon capsule endoscopy (Proc (Bayl Univ Med Cent) 2019;33:28)
Laboratory
- Assays for detection of blood in stool
- Fecal occult test detection rate is 33% (Ann Gastroenterol 2019;32:278)
- Fecal immunochemical test detection rate is 27%; very low for sessile serrated adenomas / polyps (Am J Gastroenterol 2019;114:1909, Clin Gastroenterol Hepatol 2017;15:880)
- DNA in stool
- Multitarget stool DNA test detection rate: 46% (Am J Gastroenterol 2019;114:1909)
- Multitarget stool DNA test analyzes the following (N Engl J Med 2014;370:1287):
- KRAS mutations
- Aberrant NDRG4 and BMP3 promoter methylation
- Β-actin as reference gene
- Hemoglobin (immunochemical assay)
- Positive predictive value for colorectal neoplasia: 67% (Am J Gastroenterol 2020;115:608)
- Commercial name: Cologuard
- Presence of key metabolites in urine: detection rate of adenomatous polyps: 43% (Int J Colorectal Dis 2019;34:1953)
- Iron deficiency anemia (Arab J Gastroenterol 2016;17:67)
- Elderly: 15 - 30% caused by blood loss from colon, including from polyps (PSNet: Anemia and Delayed Colon Cancer Diagnosis [Accessed 09 June 2020])
- Genetic tests for familial syndromes; examples include:
- Adenomatous polyposis: mutation in APC (classic) or MUTYH (autosomal recessive)
- Lynch syndrome: mutation in mismatch repair genes
- Peutz-Jeghers syndrome: mutation in STK11
Radiology description
- CT colonography is a validated screening test for colon polyps (World J Radiol 2016;8:472)
- CT colonography has average sensitivity of 88.8% for polyps ≥ 6 mm or colorectal carcinoma (Eur Radiol 2014;24:1049)
- Contrast screening during CT leads to better detection (odds ratio: 40.4) (Radiology 2016;280:455)
- Radiological imaging classification systems:
- Kudo: analyze pits of colonic crypt; neoplastic versus nonneoplastic (World J Gastroenterol 2014;20:12649)
- NBI International Colorectal Endoscopic (NICE): color, vascular pattern, structure of the surface (Gastroenterol Res Pract 2018;2018:7531368)
- Dutch Workgroup serrAted polypS & Polyposis (WASP) (Gut 2016;65:963, GE Port J Gastroenterol 2019;26:314):
- Based on NICE classification
- Distinguish serrated versus hyperplastic polyps
Prognostic factors
- Some prognostic factors for neoplastic polyps are listed below:
- Sex: men twice as likely to have adenomas (Best Pract Res Clin Gastroenterol 2017;31:419)
- Adenoma detection rate: 24.7% in men and 14.3% in women (Br J Cancer 2016;115:1421)
- Age: prevalence increases with age
- Prevalence is 35 - 39% in adults aged 50 - 59 versus 55 - 70% in adults aged 80+ (Best Pract Res Clin Gastroenterol 2017;31:419)
- Patients 50 years old and older are more likely to have sessile polyps and polyps in proximal colon (Arq Bras Cir Dig Apr-Jun;27:109)
- Geographic location: higher rates in Australia, New Zealand, Europe and North America; lower rates in Africa and South Central Asia (Best Pract Res Clin Gastroenterol 2017;31:419)
- Race: African Americans 76% relative risk, Hispanic 37% versus white for adenomas (Best Pract Res Clin Gastroenterol 2017;31:419)
- Sex: men twice as likely to have adenomas (Best Pract Res Clin Gastroenterol 2017;31:419)
- Serrated polyps:
- Serrated polyps: prevalence estimated to be 13 - 52% (Gut 2015;64:929, Am J Gastroenterol 2015;110:501)
- Higher risk with Helicobacter pylori infection (odds ratio: 1.71), age 50 - 75 years (odds ratio: 2.83), female (odds ratio: 1.28), white (odds ratio: 1.52), obese, smoking (odds ratio: 2.09) (Indian J Gastroenterol 2018;37:235)
- Race: African Americans 35% lower relative risk of serrated polyps, Hispanic 67% lower risk versus white (Best Pract Res Clin Gastroenterol 2017;31:419)
- Sessile serrated polyp more likely to harbor high grade dysplasia than other adenomas when there is associated invasive carcinoma (40% versus 25.8%) (Intest Res 2016;14:270)
- Sessile serrated polyps with cytological dysplasia have worse prognosis, more likely to develop into colorectal carcinoma (Gut 2016;65:437)
- Polyp recurrence:
- Sessile serrated polyp more likely to recur (27.3% reoccurred versus 3%) (Surg Endosc 2020;34:2918)
- Sex and race not predictive (Arch Intern Med 2010;170:1127)
- More likely in polyp > 3 mm (odds ratio 3.4) (Endoscopy 2019;51:253)
- More likely with immediate bleeding (Endoscopy 2019;51:253)
- More likely in same location (Rev Esp Enferm Dig 2016;108:563)
- 4x higher proximal (odds ratio: 3.5) and distal (odds ratio: 3.8) segments, 3x higher in rectum (odds ratio: 2.6) (Rev Esp Enferm Dig 2016;108:563)
- More likely with left sided polyps (Turk J Med Sci 2017;47:1370)
- More likely with villous polyps (World J Gastroenterol 2019;25:1502)
- More likely with piecemeal resection (World J Gastroenterol 2019;25:1502)
- Less likely with exercise (Cancer Prev Res (Phila) 2017;10:478)
- Prognostic factors of syndromes:
- Familial adenomatous polyposis
- Older age = worse prognosis (more likely to have colorectal carcinoma at the time of familial adenomatous polyposis diagnosis; odds ratio 4.75 for age 40 - 49 and age > 50 years versus age < 30 years (World J Gastroenterol 2016;22:4380)
- Panel of peptides can be prognostic (Clin Colorectal Cancer 2016;15:e75)
- Lynch syndrome
- MSI high tumors have better prognosis (Clin Adv Hematol Oncol 2018;16:735)
- Familial adenomatous polyposis
- Risk of developing colorectal adenocarcinoma:
- M = F (Br J Cancer 2016;115:1421)
- Adenoma leads to increased risk of colorectal adenocarcinoma (JAMA 2018;319:2021)
- Increased chance with proximal serrated polyps, large serrated polyps (Am J Gastroenterol 2015;110:501, Gut 2015;64:929)
- Removed adenomatous polyps: 0.2 - 9% malignant (Gut 1998;43:669)
Treatment
- Endoscopic resection
- For lesions of mucosa, sometimes superficial submucosa
- Reduces colorectal cancer mortality (N Engl J Med 2014;371:799)
- Indication for each technique depends on size, morphology, likelihood of submucosal invasion of lesion (Ann Gastroenterol 2017;30:592)
- Endoscopic techniques
- Standard endoscopic techniques:
- Cold snare polypectomy:
- Recommended technique for polyps 5 mm or less and for sessile polyps 6 - 9 mm (Endoscopy 2017;49:270, Gastroenterol Clin North Am 2013;42:443)
- Usually can achieve complete resection, adequate tissue for histology, low complication rates (Endoscopy 2017;49:270)
- Safer than hot techniques; less bleeding (Clin Gastroenterol Hepatol 2020;18:42)
- Hot snare polypectomy:
- Recommended for sessile polyps 10 - 19 mm, pedunculated polyps (Endoscopy 2017;49:270)
- Increased risk of immediate and delayed injury (Endoscopy 2017;49:270)
- Cold forceps biopsy:
- Most often used for diminutive lesions (1 - 5 mm)
- High retrieval rate and low complication rate (Dig Endosc 2014;26:98)
- Less likely to get complete resection compared to cold snare; takes longer to perform (Am J Gastroenterol 2013;108:1593, Gastrointest Endosc 2016;83:508)
- Useful when cold snare is not possible (Ann Gastroenterol 2017;30:592)
- Hot forceps biopsy:
- Thermal ablation of polyps with a coagulation current through an electrosurgical unit
- Destruction of polyp base makes histological diagnosis difficult (Clin Endosc 2016;49:350, J Clin Gastroenterol 2013;47:657)
- Increased risk of delayed bleeding or hypercoagulation syndrome (Clin Endosc 2016;49:350, J Clin Gastroenterol 2013;47:657)
- Considered to be less effective and less safe than cold snare (World J Gastroenterol 2017;23:328)
- Cold snare polypectomy:
- Advanced endoscopic techniques:
- Endoscopic mucosal resection:
- Technique used for removal of large flat or sessile polyps
- “Inject and cut” is a snare resection after saline injection into the submucosal wall
- Alternatives: cap assisted endoscopic mucosal resection, underwater endoscopic mucosal resection for fibrotic tissue, cold snare endoscopic mucosal resection for polyps > 1 cm based on single center retrospective studies (Gastrointest Endosc 2012;75:1086, Gastrointest Endosc 2015;81:1238, Endosc Int Open 2017;5:E184, Endosc Int Open 2015;3:E508)
- For flat large polyps, size is main predictor for recurrence (Digestion 2016;93:311)
- Endoscopic submucosal dissection:
- Mainly considered for complex lesions
- After submucosal injection, needle type ESD knife is used for circumferential incision and then submucosal layer is dissected; hybrid technique uses knife with snare (Gastrointest Endosc 2017;86:74)
- Allows en bloc resection versus endoscopic mucosal resection (Clin Endosc 2016;49:454)
- Higher risk of perforation and need of surgery versus endoscopic mucosal resection (Clin Endosc 2016;49:454)
- Lower en bloc and R0 resection rates in non-Asian countries versus Asian countries (Gastrointest Endosc 2017;86:74)
- The data in lesions > 50 mm show lower R0 resection rate and significantly increased procedure times (Endosc Int Open 2016;4:E895)
- Endoscopic mucosal resection:
- Standard endoscopic techniques:
Gross description
- Paris classification based on explicit recognition (Endoscopy 2005;37:570)
- Polypoid type:
- Protrudes at least 2.5 mm above mucosal layer
- Sessile: no stalk (o-Is)
- Pedunculated: with stalk, may be due to traction on the mass (o-Ip)
- Semipedunculated (o-Isp)
- Nonpolypoid type:
- Less than 2.5 mm above mucosal layer
- Slightly elevated (o-IIa)
- Flat (o-IIb)
- Slightly depressed lesions (o-IIc)
- Excavated / ulcerated: o-III (Ann Gastroenterol 2017;30:592)
- Polypoid type:
Microscopic (histologic) description
- Generally depends on type of polyp (see specific topics for details)
- Histology of submucosal lifting agents used during polypectomy
- Some examples include ORISE and Eleview
- Histologic appearance of lifting agents is temporally dependent, ranging from basophilic bubbly amorphous material (early) to eosinophilic hyalinized globules or ribbons (late)
- Can mimic amyloid but differentiated based on presence of foreign body giant cell reaction to lifting agent that is not polarizable and Congo red negativity (Am J Surg Pathol 2020;44:793, Am J Clin Pathol 2020;153:630)
