Pretty but probably poisonous

December 03, 2015 By: Bjorn Rembacken

Figure 1 | A polyp found in the rectum of a middle-aged man who was undergoing colonoscopy as part of a polyp surveillance programme.

Pretty but probably poisonous    

What is the most likely histology of the lesion?

The beautiful polyp shown in the photograph (figure 1) was found in the rectum of a middle-aged man who was on a polyp surveillance programme.

WHAT IS THE MOST LIKELY HISTOLOGY OF THE LESION?

a)    Hyperplastic polyp

b)    Tubular adenoma

c)     Tubulovillous adenoma

d)    Villous adenoma

e)    Traditional serrated adenoma

Discussion

You could be forgiven for guessing that this is a villous adenoma with almost ridiculously long villi. The lesion actually proved to be a traditional serrated adenoma (TSA).

TSAs are part of the complex family of serrated lesions, which currently includes hyperplastic polyps, sessile serrated lesions (SSLs), sessile serrated adenomas (SSAs), TSAs and mixed hyperplastic- adenomatous lesions.

Some 30 years ago, there were only two types of serrated lesion—the hyperplastic polyp and the mixed hyperplastic- adenomatous polyp. In 1990, the TSA was first described by Longare and Fenoglio-Preiser;1 however, there was a period of confusion until Torlakovic et al. reviewed the serrated polyp and gave it its modern name.2 Hyperplastic polyps were not thought to have any malignant potential, but in 1996 Torlakovic and Snover3 reported that the hyperplastic polyps found in hyperplastic polyposis syndrome (now called serrated polyposis syndrome4) were different to ‘normal’ hyperplastic polyps and that they had a malignant potential.

The TSA is a mysterious entity, only accounting for about 1% of colorectal polyps.5 Endoscopically, they can appear as exaggerated tubulovillous adenomas or as villous adenomas. Because of their variable appearance, both endoscopically and histologically, there is no agreement on their molecular features and study findings are conflicting. Hopefully, immunohistochemistry will come to our aid in the future!

It is uncertain how TSAs contribute to cancers arising from the serrated pathway,6 which are thought to give rise to at least the 7–12% of “cancers with a serrated morphology”.7 Serrated carcinomas have a poor prognosis and are more common in the elderly. As more than half of serrated carcinomas arise in the caecum or ascending colon, it is tempting to assume that they originate from hard-to-see serrated precursor lesions. There is some support for this notion because interval cancers are four times more likely than non-interval cancers to be of the CpG island methylator phenotype (CIMP)8 and to show some degree of microsatellite instability, both of which are features of serrated-pathway cancers.9,10 Conversely, it is possible that the one-third of serrated cancers that are found in the distal colon arise from TSAs.11

The understanding that some aggressive cancers arise from an alternative pathway to the classic adenoma–carcinoma pathway is a challenge when deciding on surveillance after the removal of a serrated lesion. The US multisociety taskforce on colorectal cancer12 and the European Society of Gastrointestinal Endoscopy13 have both published surveillance guidelines for serrated lesions with some agreement (table 1).

 

References 

  1. Longacre TA and Fenoglio-Preiser CM. Mixed hyperplastic adenomatous polyps/serrated adenomas. A distinct form of colorectal neoplasia. Am J Surg Pathol 1990; 14; 524–537.
  2. Torlakovic E, Skovlund E, Snover DC, et al. Morphologic reappraisal of serrated colorectal polyps. Am J Surg Pathol 2003; 27; 65–81.
  3. Torlakovic E and Snover DC. Serrated adenomatous polyposis in humans. Gastroenterology 1996; 110; 748–755.
  4. Rosty C, Parry S and Young JP. Serrated polyposis: an enigmatic model of colorectal cancer predisposition. Patholog Res Int 2011. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3109311
  5. Higuchi T, Sugihara K and Jass JR. Demographic and pathological characteristics of serrated polyps of colorectum. Histopathology 2005; 47; 32–40.
  6. Jass JR. Classification of colorectal cancer based on correlation of clinical, morphological and molecular features. Histopathology 2007; 50; 113–130.
  7. Bosman FT, World Health Organization and International Agency for Research on Cancer. World Health Organization classification of tumours of the digestive system, 4th edn. Lyon: IARC, 2010.
  8. Weisenberger DJ, Siegmund KD, Campan M, et al. CpG island methylator phenotype underlies sporadic microsatellite instability and is tightly associated with BRAF mutation in colorectal cancer. Nat Genet 2006; 38: 787–793.
  9. Sawhney MS, Farrar WD, Gudiseva S, et al. Microsatellite instability in interval colon cancers. Gastroenterology 2006; 131: 1700–1705.
  10. Arain MA, Sawhney M, Sheikh S, et al. CIMP status of interval colon cancers: another piece to the puzzle. Am J Gastroenterol 2010; 105: 1189–1195.
  11. Makinen MJ. Colorectal serrated adenocarcinoma. Histopathology 2007; 50; 131–150.
  12. Lieberman DA, Rex DK, Winawer SJ, et al. Guidelines for colonoscopy surveillance after screening and polypectomy: a consensus update by the US Multi-Society Task Force on Colorectal Cancer. Gastroenterology 2012; 143: 844–857.
  13. Hassan C, Quintero E, Dumonceau JM, et al. Post-polypectomy colonoscopy surveillance: European Society of Gastrointestinal Endoscopy (ESGE) Guideline. Endoscopy 2013; 45: 842–851.

Answer

Correct answer: e.

 

 

About the author

Bjorn Rembacken is at Leeds Teaching Hospitals NHS Trust, Leeds, UK. He was born in Sweden and qualified from Leicester University in 1987. He undertook his postgraduate education in Leicester and in Leeds. His MD was dedicated to inflammatory bowel disease. Dr Rembacken was appointed Consultant Gastroenterologist, Honorary Lecturer at Leeds University and Endoscopy Training Lead in 2005. Follow Bjorn on Twitter @Bjorn_Rembacken

 

Comments

Oscar Castillo, February 01, 2016 14:05
Villous adenoma
Nerida Dhigoi, January 18, 2016 15:17
Villous adenoma
lidziya tarasenka, January 17, 2016 12:24
e) TSA
Ahmed Gabr, December 16, 2015 00:28
I would go for E
Sergey Polishchuk, December 15, 2015 19:42
d) Villous adenoma
Gueorgui, December 13, 2015 22:57
E) TSA
Iles Raluca, December 13, 2015 12:23
Traditional serrated adenoma with tubulovillous morphology.
Diana Aksionova, December 12, 2015 13:44
d
Irina Korytko, December 12, 2015 02:46
vote for D.
Mohamed, December 11, 2015 23:14
d villous adenoma

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