Overview of the International Classification of Diseases for Oncology, 4th Edition (ICD-O-4)
This paper summarises the rationale and content of the new 4th edition (ICD-O-4) of the International Classification of Diseases for hashtag#Oncology (ICD-O). ICD-O is the longstanding system used byhashtag#CancerRegistries for coding tumours according to their site of origin (topography), microscopic appearance or histology, behaviour and grade, and is optimal for use in cancer registries. ICD-O-4 provides an improved structure of unique codes to existent and newly defined tumour entities and has been harmonised with the International Classification of Diseases 11th Edition (ICD-11).
After a period of consultation with cancer registries, ICD-O-4 is published following a review of the fifth Edition of the World Health Organization Classification of Tumours (WCT) which recognised several new tumour entities and introduced certain tumours that were molecularly defined with clinically relevant molecular profiles. Upon its completion, there was a compelling need for an updated ICD-O that would allow for unique codes to be assigned to the newly-defined tumour entities, facilitating the accurate coding of tumours included in the current and future editions of the WCT.
Included as supplementary material are the ICD-O-4 main tables (containing 414 topography and 2450 morphology codes) and the list of changes from ICD-O-3.2.
The finalised ICD-O-4 topography and morphology tables will be available on the IARC WCT website while the official ICD-O-4 publication (with WHO) is in preparation.
Znaor A, Rous B, Levy GG, Watanabe R, Jakob R, Krpelanova E, Wijesinghe HD, Puspanathan P, Cree IA, Bray F, Lokuhetty D. The International Classification of Diseases for Oncology, 4th Edition (ICD-O-4): An overview. Cancer Epidemiol. 2026 Jan 22;101:102989. doi: https://lnkd.in/eDiyyfsB. Epub ahead of print. PMID: 41576584
