CADM1 (cell adhesion molecule 1) is a multifunctional immunoglobulin superfamily cell adhesion molecule that serves as both a tumor suppressor and diagnostic marker depending on cellular context 1. The protein functions primarily through homophilic dimerization on cell membranes and association with actin-binding proteins and scaffold proteins containing PDZ motifs, forming ternary complexes essential for cell adhesion and epithelial structure formation 1. CADM1 controls actin cytoskeleton assembly and regulates extracellular matrix adhesion, particularly in mast cells where it accounts for 46% of surface KIT levels and 31% of F-actin polymerization 2. The molecule exhibits tissue-specific expression patterns and opposing roles in different cancers: it acts as a tumor suppressor in epithelial cancers where expression is often lost 1, but is overexpressed in adult T-cell leukemia/lymphoma serving as a diagnostic marker 1. CADM1 also functions as a tumor antigen recognized by NK cells and CD8+ T cells through heterophilic interaction with CRTAM 1. In aldosterone-producing adenomas, somatic CADM1 mutations disrupt gap junction communication, leading to increased aldosterone production and reversible hypertension 3. Additionally, CADM1 serves as an embryonic skeletal stem cell marker and is utilized as a DNA methylation biomarker for cervical and anal cancer screening 45.