The International Classification of Diseases for Oncology (ICD-O) is a domain specific extension of the International Classification of Diseases (ICD) for Tumour diseases. This classification is widely used by Cancer Registries for coding the site (topography) and the histology (morphology) of neoplasms, usually obtained from a pathology report. The International Classification of Diseases for Oncology (ICD-O) is published by the World Health Organisation.

Further information is available from the World Health Organisation website.