Mucinous Colon Adenocarcinoma and Treatment Response: A Critical Review of Prognostic Associations and Emerging Predictive Evidence

Mucinous adenocarcinoma (MAC) is a distinct colorectal cancer subtype characterized by specific clinicopathological and molecular features and a propensity for peritoneal dissemination. However, whether mucinous histology primarily represents a prognostic phenotype or independently modifies response to anticancer treatment remains uncertain. This critical narrative review evaluated the therapeutic significance of mucinous histology across localized and metastatic colon cancer. A structured PubMed/MEDLINE search was conducted from database inception through 14 September 2026 using MeSH terms and title/abstract keywords related to mucinous histology, colon or colorectal adenocarcinoma, and treatment-related outcomes. The primary search identified 2896 records and was supplemented by targeted searches and reference-list screening. Evidence was interpreted using a four-level framework distinguishing prognostic association, treatment-response association, differential treatment effect, and validated predictive biomarkers. In localized disease, available evidence supports a clinically meaningful benefit from adjuvant chemotherapy in stage III MAC, whereas evidence in stage II disease does not support treatment modification based on histology alone. In metastatic disease, historical cohorts report lower objective response to cytotoxic chemotherapy, but current evidence does not establish intrinsic MAC-specific chemotherapy resistance. Retrospective anti-VEGF and anti-EGFR studies provide treatment-response signals without demonstrating validated histology-specific predictive effects. In dMMR/MSI-H disease, immune-checkpoint blockade remains guided by molecular status rather than mucinous morphology. Peritoneal-predominant dissemination further complicates response assessment and interpretation of locoregional treatment outcomes. Current evidence does not support mucinous histology as a stand-alone predictive biomarker for treatment selection. MAC should instead be interpreted as a contextual clinicopathological modifier alongside disease stage, resectability, metastatic distribution, and validated molecular biomarkers.