The International Classification of Diseases for Oncology (ICD-O) is a domain-specific extension of the International Statistical Classification of Diseases and Related Health Problems for tumor diseases. This classification is widely used by cancer registries.
It is currently in its third revision (ICD-O-3). ICD-10 includes a list of morphology codes. They stem from ICD-O second edition (ICD-O-2) that was valid at the time of publication.