Colorectal Carcinoma Pathology and Molecular Characteristics

Colorectal carcinoma encompasses a spectrum of epithelial malignancies arising in the large bowel, distinguished by diverse histological subtypes and distinct molecular pathways. Conventional adenocarcinoma remains the predominant form, but rarer variants—including medullary, mucinous, signet-ring, adenosquamous and rhabdoid carcinomas—exhibit unique morphological and genetic features with implications for prognosis and therapy. Tumourigenesis often follows one of three principal routes: chromosomal instability (CIN), microsatellite instability (MSI) and the CpG island methylator phenotype (CIMP). CIN is typified by aneuploidy and frequent TP53 and APC mutations, whereas MSI arises from defective mismatch repair, yielding high mutational burdens and sensitivity to immune checkpoint blockade. CIMP-positive tumours display widespread promoter hypermethylation, frequently accompanied by BRAF V600E alterations. Additional oncogenic drivers include KRAS, PIK3CA and alterations in Wnt/β-catenin signalling. The tumour microenvironment—encompassing immune infiltrates and stromal interactions—further influences invasion, metastatic spread and response to targeted therapies. Advances in molecular subtyping, prognostic models and personalised treatment strategies underscore the global significance of integrating pathology with genomic profiling for improved patient outcomes.

Research from Nature Portfolio

Recent studies have refined prognostic assessment for rare histotypes by integrating clinicopathological variables into predictive nomograms. One large population-based analysis developed and validated models for medullary carcinoma of the colon, identifying age, nodal stage, metastatic status, surgical intervention, chemotherapy completion and tumour size as independent predictors of overall survival. These tools demonstrate robust calibration and discrimination, offering a framework for individualised clinical decision-making. Complementing this, cohort analyses of medullary adenocarcinoma have revealed a rising incidence in contrast to declining rates of conventional adenocarcinoma. Distinct molecular profiles—characterised by high MSI prevalence, right-sided predominance and frequent lymphovascular invasion—were documented. Stratification by laterality uncovered worse outcomes in left-sided medullary tumours, emphasising the need for side-specific management and further exploration of molecular determinants driving these differences.

Colorectal Carcinoma Pathology and Molecular Characteristics publication trend

The graph below shows the total number of articles in colorectal carcinoma pathology and molecular characteristics across all publications each year (not limited to Nature Index journals).

Technical terms

Chromosomal instability (CIN): widespread gain or loss of chromosomes leading to aneuploidy.

CpG island methylator phenotype (CIMP): extensive promoter hypermethylation silencing tumour suppressor genes.

Microsatellite instability (MSI): hypermutation resulting from defective DNA mismatch repair.

Nomogram: graphical risk prediction tool integrating multiple clinical and pathological factors.

Medullary carcinoma: poorly differentiated subtype with syncytial growth, abundant lymphoid stroma and high MSI.

Adenosquamous carcinoma: mixed glandular and squamous differentiation associated with aggressive behaviour.

Rhabdoid carcinoma: rare, highly aggressive tumour with SMARCB1 loss and characteristic cytoplasmic inclusions.

MAPK pathway: mitogen-activated protein kinase cascade regulating cell proliferation and survival, often driven by BRAF or KRAS mutations.

References

1. Morphology and Molecular Features of Rare Colorectal Carcinoma Histotypes. Cancers (2019).
2. Risk factor analysis and nomogram development and verification for medullary carcinoma of the colon using SEER database. Scientific Reports (2024).
3. Sidedness determines clinical characteristics and survival outcomes in medullary adenocarcinoma of the colon. Scientific Reports (2021).
4. The chromatin remodelling component SMARCB1/INI1 influences the metastatic behavior of colorectal cancer through a gene signature mapping to chromosome 22. Journal of Translational Medicine (2013).
5. Loss of Primary Cilia Potentiates BRAF/MAPK Pathway Activation in Rhabdoid Colorectal Carcinoma: A Series of 21 Cases Showing Ciliary Rootlet CoiledCoil (CROCC) Alterations. Genes (2023).
6. Colorectal adenosquamous carcinoma: genomic profiling of a rare histotype of colorectal cancer. Virchows Archiv (2023).