Abstract
BACKGROUND: The International Classification of Diseases (ICD) and the International Classification of Diseases for Oncology (ICD-O) are both widely used global classification systems. In 2018, the initial release of the ICD-11 was published by the World Health Organization (WHO), integrating the morphology section of the ICD-O. METHODS: This paper aims to provide potential ICD-11 users with a profound understanding of the neoplasm classifications of the ICD-11 by analysing the differences and relationships between the ICD-11 and ICD-O in terms of the coding framework, compatibility and intelligence level. RESULTS: The ICD-11 and ICD-O have remarkable differences in coding structure. Compared to the ICD-O, the ICD-11 has the following advantages: adding histopathology to the stem codes, obtaining a meaningful minimum amount of information through stem codes for statistics, supporting the usage of ICD-O morphology categories and capturing clinical details via extension codes for multiaxial coding. In addition, the rich Foundation Component, linearization derived from the Foundation Component and updating mechanism all support the compatibility of the ICD-11 with other classification systems. Notably, the WHO provides terminology coding with a smart coding tool, and coding in the ICD-11 can draw on statistical codes and uniform resource identifiers (URIs) simultaneously. CONCLUSIONS: The ICD-11 represents a novel classification system with distinguishing features that include facilitating statistics, multiaxial coding, coding granularity, compatibility and intelligence. These features enable the ICD-11 to be more powerful for neoplasm coding than the ICD-O and basically meet the needs of stakeholders.