Histomorphological features of
colorectal cancers (CRC) represent valuable prognostic indicators for clinical decision making. The invasive margin is a central feature for prognostication shaped by the complex processes governing
tumor-host interaction. Assessment of the
tumor border can be performed on standard
paraffin sections and shows promise for integration into the diagnostic routine of gastrointestinal pathology. In aggressive CRC, an extensive dissection of host tissue is seen with loss of a clear
tumor-host interface. This pattern, termed "infiltrative
tumor border configuration" has been consistently associated with poor survival outcome and early disease recurrence of CRC-patients. In addition, infiltrative
tumor growth is frequently associated with presence of adverse clinicopathological features and molecular alterations related to aggressive
tumor behavior including BRAFV600 mutation. In contrast, a well-demarcated "pushing"
tumor border is seen frequently in CRC-cases with low risk for nodal and distant
metastasis. A pushing border is a feature frequently associated with
mismatch-repair deficiency and can be used to identify patients for molecular testing. Consequently, assessment of the
tumor border configuration as an additional prognostic factor is recommended by the AJCC/UICC to aid the TNM-classification. To promote the assessment of the
tumor border configuration in standard practice, consensus criteria on the defining features and method of assessment need to be developed further and tested for inter-observer reproducibility. The development of a standardized quantitative scoring system may lay the basis for verification of the prognostic associations of the
tumor growth pattern in multivariate analyses and clinical trials. This article provides a comprehensive review of the diagnostic features, clinicopathological associations, and molecular alterations associated with the
tumor border configuration in early stage and advanced CRC.