Abstract
<title>Abstract</title> <p> <bold>Background</bold> Global childhood and adolescent cancer burden estimation is limited by inconsistent diagnostic classification systems. ICCC‑3 is the benchmark for pediatric cancer research, but large registries mainly use ICD‑10, which cannot be directly matched to ICCC‑3. A unified mapping framework is required to accurately quantify disease burden and enable cross‑database data comparison. <bold>Methods</bold> We used pediatric cancer incidence data from the US registries in CI5 Volume XII, which provides dual coding in ICD-10 and ICCC-3. We developed a three-tier ICD-10 to ICCC-3 mapping strategy: (1) direct mapping to main diagnostic groups; (2) subgroup mapping for lymphoid and hematopoietic neoplasms; and (3) manual mapping for the other subgroups. <bold>Results</bold> We identified 77,236 pediatric cancer cases coded in ICD-10 and 77,152 cases coded in ICCC-3. Near-perfect concordance (CR ≈ 1.00) was observed for retinoblastoma, brain and CNS tumors, renal tumors, and hepatic tumors. Over-mapping was noted for epithelial neoplasms/melanomas (CR = 1.24), bone tumors (CR = 1.11), and leukemias (CR = 1.07), while under-mapping occurred for neuroblastomas (CR = 0.67), germ cell tumors (CR = 0.72), soft tissue sarcomas (CR = 0.87), lymphomas (CR = 0.88), and unspecified malignant neoplasms (CR = 0.47). For lymphoid and hematopoietic neoplasms, an ICD-O-3–mediated crosswalk enabled subgroup mapping with enhanced specificity. However, for most other subgroups, precise one-to-one mapping was not feasible, with the exception of hepatoblastoma (C22.2). <bold>Conclusion</bold> This study provides the first systematic mapping of ICD-10–coded pediatric cancer cases to ICCC-3 categories. The mapping demonstrated reliable correspondence for lymphoid and hematopoietic neoplasms subgroups. Concordance for certain solid tumors remained suboptimal due to limitations of ICD-10 in capturing morphological details. </p>