Clinical Scorecard: Case Study: Concurrent Colorectal Adenocarcinomas Exhibiting Divergent Mismatch Repair Status: Insights into Lynch-like Syndrome and Serrated Pathway Correlation
At a Glance
Category
Detail
Condition
Synchronous colorectal adenocarcinomas with discordant mismatch repair (MMR) status
Key Mechanisms
Distinct tumorigenic pathways including Lynch-like syndrome (dMMR without germline mutations) and serrated pathway (pMMR), with lesion-specific molecular heterogeneity
Target Population
Patients diagnosed with synchronous colorectal cancers exhibiting intertumoral MMR heterogeneity
Care Setting
Oncology and surgical departments managing colorectal cancer patients requiring molecular profiling and individualized treatment planning
Key Highlights
Synchronous colorectal cancers (SCRCs) can present with discordant MMR status, complicating diagnosis and treatment.
Lesion-specific molecular profiling combined with regional lymph node MMR phenotyping guides precise surgical and adjuvant therapy decisions.
Lynch-like syndrome is characterized by dMMR tumors without germline MMR mutations, negative BRAF V600E mutation, and absence of MLH1 promoter methylation.
Guideline-Based Recommendations
Diagnosis
Perform comprehensive molecular testing on each synchronous lesion, including MMR immunohistochemistry, BRAF V600E mutation, MLH1 promoter methylation, and germline NGS for MMR genes.
Assess regional metastatic lymph nodes for MMR phenotype to evaluate invasive potential of each tumor.
Consider diagnosis of Lynch-like syndrome when dMMR tumors lack germline MMR mutations, BRAF mutation, and MLH1 methylation.
Management
Adopt individualized treatment strategies based on lesion-specific molecular profiles and lymph node MMR status.
Use adjuvant chemoradiotherapy (e.g., CAPEOX regimen) tailored to the tumor’s molecular characteristics and metastatic potential.
Implement risk-adapted surgical decision-making informed by molecular heterogeneity.
Monitoring & Follow-up
Conduct regular follow-up with imaging and clinical assessment to monitor for recurrence or metastasis.
Evaluate patient quality of life during and after treatment.
Risks
Risk of erroneous treatment if molecular testing is limited to a single lesion in SCRCs due to intertumoral heterogeneity.
Potential for higher metastatic potential in pMMR tumors compared to dMMR tumors in synchronous lesions.
Patient & Prescribing Data
67-year-old female with synchronous ascending colon dMMR adenocarcinoma (Lynch-like syndrome) and rectal pMMR adenocarcinoma adjacent to sessile serrated lesion
Adjuvant CAPEOX-based chemoradiotherapy was administered guided by lesion-specific molecular findings and lymph node MMR phenotyping, resulting in no recurrence or metastasis at 24 months and satisfactory quality of life.
Clinical Best Practices
Perform lesion-specific molecular characterization for all synchronous colorectal tumors to detect intertumoral heterogeneity.
Incorporate regional metastatic lymph node MMR phenotyping to assess tumor invasive potential and guide adjuvant therapy.
Use a multidisciplinary approach integrating molecular diagnostics, pathology, surgery, and oncology for individualized patient management.
Recognize Lynch-like syndrome as a distinct clinical entity requiring specific diagnostic criteria and management.
Avoid reliance on single-lesion molecular testing in synchronous colorectal cancers to prevent misclassification and suboptimal treatment.
