Abstract
The Molecular Characterization Initiative (MCI), a key effort of the National Cancer Institute's Childhood Cancer Data Initiative (CCDI), was launched in 2022 in collaboration with the Children's Oncology Group (COG) to bring comprehensive genomic and molecular profiling to children, adolescents, and young adults diagnosed with cancer. The MCI provides paired tumor and germline molecular testing, with results returned to clinicians to inform care. Deidentified data are made available to the research community through the CCDI Data Ecosystem to facilitate the discovery of new treatment strategies. This commentary outlines the MCI's development, key accomplishments to date, and its role in laying the foundation for standardized clinical diagnostics in pediatric oncology.