Mucinous carcinoma of the rectum a distinct clini

Authors: M Chand S Yu R I Swift G Brown

Publish Date: 2013/12/11

Volume: 18, Issue: 4, Pages: 335-344

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Abstract

The definition of mucinous tumours relies on quantification of the amount of mucus produced by neoplastic cells within the rectum This has changed over the years to include varying degrees of mucin production The inconsistency of diagnosis has led to conflicting reports in the literature regarding clinical outcomes and treatment response A universally accepted definition and improved imaging and surgical techniques in the last decade are now challenging the traditional view of these tumours The aim of this review was to present the current evidence on the clinicopathological characteristics of mucinous tumours of the rectumA systematic review was conducted using Preferred Reporting for Systematic Reviews and MetaAnalyses guidelines A literature search was performed using the Ovid SP to search both EMBASE and MEDLINE databases Google Scholar and PubMed to find all studies relating to mucinous carcinoma of the rectum The search dates were between 1 January 1965 and 1 March 2013Mucinous tumours comprise 5–20  of all rectal cancers and commonly present at a more advanced stage and in younger patients They are readily identified on MRI and the diagnosis is confirmed on histological analysis demonstrating more than 50  of extracellular mucin within the tumour complex They carry an overall worse prognosis compared to adenocarcinoma of the same stage The response to oncological treatment remains controversialMucinous tumours of the rectum are less well understood than nonmucinous adenocarcinoma This is due to the inconsistent histopathological definitions of the past making comparison of clinical outcome data difficult They remain challenging to treat and are associated with a poor prognosis A universally accepted definition and the role of imaging techniques such as MRI to accurately detect mucinous tumours are likely to lead to a better understanding of these cancersMucinous carcinoma is a specific morphological subtype of rectal cancer It is characterised by an abundance of extracellular mucin secreted by overactive neoplastic acinar cells Mucinproducing tumours have been described in other sites such as breast prostate ovary and pancreas and share some generic characteristics 1 The abundance of mucin within the tumour complex gives it a unique appearance both histologically and radiologically Contrast this with signet cell carcinomas which are a specific type of mucinproducing tumour in which single neoplastic cells demonstrate large amounts of intracytoplasmic mucin that results in displacement of the nucleiOver the years there has been debate on the precise histological definition of mucinous tumours which has made interpretation of studies problematic The current accepted definition initially proposed by Jass is based on the presence of a minimum of 50  of mucin to tumour volume 2 Previous studies have used varying proportions of mucin to define these tumours 3 4 They represent 5–20  of all colorectal cancers 5 6 7 8 and are generally considered to have a worse prognosis than nonmucinous tumours of the rectum Furthermore they are also suggested to have a limited response to oncological treatmentsAn electronic search was carried out using MEDLINE 1965–2013 EMBASE 1980–2013 CINAHL 1982–2013 and the Cochrane library databases The following medical subject heading MeSH terms and keywords were used as follows The keywords “mucinous” “mucoid” “colloid” “colorectal” “rectal” “tumours/tumors” “cancer” were used in combination The “related articles” function was used to broaden the search and all abstracts studies and citations retrieved were scanned for subject relevance The latest date of this search was 1 March 2013

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