Mucinous carcinoma of the rectum: a distinct clinicopathological entity

Abstract

Purpose 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 rectum. Methods A systematic review was conducted using Preferred Reporting for Systematic Reviews and Meta-Analyses 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 2013. Results Mucinous 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 controversial. Conclusion Mucinous tumours of the rectum are less well understood than non-mucinous 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 cancers.

Prognostic Implications of Mucinous Differentiation in Metastatic Colorectal Carcinoma Can Be Explained by Distinct Molecular and Clinicopathologic Characteristics

“…The most common CRC histologic subtypes include adenocarcinoma, mucinous, signet ring cell, medullary, and micropapillary, however there are other rare histopathological variants [1]. The mucinous subtype accounts for 5% to 20% of all CRCs [2], and has been defined by the presence of abundant extracellular mucous which contributes to more than 50% of tumor volume [3]. …”

The potential predictive value of MRI and PET-CT in mucinous and nonmucinous rectal cancer to identify patients at high risk of metastatic disease

“…7,8 Mucinous carcinoma (MC) represents a subtype of rectal carcinoma; it is defined by high signal intensity in T 2 weighted (T2w) imaging, which identifies mucin pools in rectal carcinomas with a high accuracy. [10][11][12][13][14] Most studies have found that patients with MC have a poorer prognosis than those with non-mucinous (NMC) rectal cancer, [15][16][17][18] although some studies found no correlation between mucinous histotype and prognosis. 19,20 Recently, Hugen et al 21 performed a large population-based study in which multivariate analysis showed no differences in overall survival in MC and NMC except when the tumour was located in the rectum.…”

Mucinous carcinoma is a predictive factor for the risk of open conversion from laparoscopic colectomy in colorectal cancer

“…Mucinous carcinoma is diagnosed if the tumor cells produce mucin that aggregates into pools or lakes, occupying > 50% of the tumor [25]. As the definition of mucinous carcinoma has varied according to the amount of mucus produced by neoplastic cells within the rectum over the years, mucinous tumors of the rectum are less well understood than non-mucinous tumors [10]. Several studies have observed that mucin has a pressure effect that causes dissemination of cancer cells into the peritoneal cavity [26][27][28].…”

“…Hyngstrom et al [9] found that muci-nous cancer located in the rectum showed worse survival outcomes with a hazard ratio (HR) of death of 1.22, but not for those located in the colon (HR, 1.03). Chand et al [10] explained that mucinous carcinoma in the rectum has a more aggressive behavior than mucinous carcinoma in the colon because of the anatomical location and the immediate effect of the narrow pelvic cavity. In the present study, the association between the mucinous histologic type and open conversion in low colorectal cancer can be explained by the unique clinicopathologic behavior of mucin.…”

“…Nevertheless, when mucinous carcinoma presents in the rectum, it behaves more aggressively [9]. A study suggests that the reason for aggressiveness when located in the rectum may be due to the anatomical effect of the pelvic cavity [10].…”