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Updated: Nov 6, 2025

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An Insight Into the Driver Mutations and Molecular Mechanisms Underlying Mucinous Adenocarcinoma of the Rectum

Ian S Reynolds1,2, Emer O'Connell1,2, Michael Fichtner2,3

  • 1Department of Colorectal Surgery, Beaumont Hospital, Dublin, Ireland.

Diseases of the Colon and Rectum
|May 6, 2021
PubMed
Abstract

Insights

Mucinous rectal tumors show a higher rate of mismatch repair deficiency compared to other rectal adenocarcinomas. Further research into chromosomal instability and mucin barrier effects is needed for this subtype.

Area of Science:

  • Oncology
  • Genomics
  • Molecular Biology

Background:

  • Mucinous adenocarcinoma of the rectum constitutes 10% of rectal cancers, exhibiting poor response to neoadjuvant chemoradiotherapy and reduced overall survival.
  • Limited genomic research exists for this specific histological subtype, necessitating further investigation.

Purpose of the Study:

  • To determine the mismatch repair deficiency rate in mucinous rectal adenocarcinoma.
  • To identify driver mutations in mucinous rectal adenocarcinoma.
  • To compare these findings with rectal adenocarcinoma not otherwise specified (NOS).

Main Methods:

  • Immunohistochemistry was used to assess mismatch repair status.
  • Next-generation sequencing (MiSeq V3 platform) was employed to identify mutations in oncogenes and tumor suppressor genes.
  • Tumor samples were analyzed from a biobank across two tertiary referral centers.

Main Results:

  • The study included 33 mucinous rectal adenocarcinoma cases and 100 rectal adenocarcinoma NOS cases.
  • A significantly higher mismatch repair deficiency rate was observed in mucinous adenocarcinoma (12.1%) compared to adenocarcinoma NOS (2.0%, p=0.04).
  • Mutation frequencies for most oncogenes and tumor suppressor genes, including KRAS and BRAF, were similar between the two cohorts. No significant differences in recurrence-free or overall survival were noted.

Conclusions:

  • Mucinous rectal tumors predominantly follow the chromosomal instability pathway.
  • The mucin barrier may play a role in resistance to chemoradiotherapy.
  • Further transcriptomic, proteomic, and mucin barrier analyses are recommended to understand resistance mechanisms.

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