The Biological Basis of the Merlin <scp>CP</scp> ‐ <scp>GEP</scp> Assay: Integrin Signaling and Early Metastatic Competence in Cutaneous Melanoma

The recent inclusion of the Merlin clinicopathologic-gene expression profile (CP-GEP) assay in the National Comprehensive Cancer Network (NCCN) Melanoma Guidelines represents an important milestone in the clinical integration of molecular testing for cutaneous melanoma. Unlike earlier melanoma gene expression profile (GEP) assays, which focused primarily on prognostic risk stratification, CP-GEP was specifically developed to predict sentinel lymph node (SLN) metastasis risk by identifying early metastatic competence within primary melanomas, with additional prognostic utility. This review discusses the biological evidence supporting CP-GEP and examines how unbiased transcriptomic discovery converged with established insights from cancer cell biology, integrin signaling, focal adhesions, and extracellular matrix (ECM) remodeling to shape its conceptual framework. We further discuss how CP-GEP captures a transformation-associated biological state centered on an integrin- and TGF-β-dependent signaling axis (ITGB3, TGFBR1) that promotes pericellular proteolysis and ECM remodeling (PLAT, SERPINE2, LOXL4), inflammatory and angiogenic signaling (CXCL8, GDF15), and melanocytic lineage identity (MLANA). Collectively, these genes identify a dissemination-competent phenotype that is detectable within primary tumors before clinically apparent metastasis. Overall, the biological framework supporting CP-GEP reinforces the concept that altered adhesion signaling and ECM remodeling are central drivers of early melanoma metastasis and represent clinically actionable biomarkers for individualized melanoma management.