CEACAM18 is a cell adhesion molecule belonging to the carcinoembryonic antigen-related cell adhesion molecule (CEACAM) family, which comprises at least 12 members with diverse tissue expression patterns 1. The protein mediates both heterophilic and homophilic cell-cell adhesion through plasma membrane interactions. CEACAM18 represents an evolutionarily conserved gene with orthologs identified across mammalian species (mouse, rat, and human) located at syntenic chr19 positions 2. Notably, CEACAM18 functions as a framework gene within the mammalian CD33-related Siglec locus, having seeded the evolution of the CD33rSiglec gene cluster through ancient large-scale inverse duplication events occurring over 180 million years ago 3. The CEACAM family exhibits tissue-specific expression patterns suggesting diversified biological functions in controlling tissue homeostasis, immune responses, and host-pathogen interactions 2. While CEACAM5 (CEA) has established clinical utility as a tumor biomarker since 1965, the broader CEACAM family, including CEACAM18, has emerging relevance in tumor immunotherapy applications 1. However, specific functional roles and clinical significance of CEACAM18 individually remain insufficiently characterized in the provided literature.