International Classification of Diseases for Oncology

Now in its third edition, the INTERNATIONAL CLASSIFICATION OF DISEASES FOR ONCOLOGY (ICD-O) has been used for nearly 25 years as the standard tool for coding diagnoses of neoplasms in tumour and cancer registrars and in pathology laboratories. ICD-O is a dual classification with coding systems for both topography and morphology. The topography code describes the site of origin of the neoplasm and uses the same 3-character and 4-character categories as in the neoplasm section of Chapter II, ICD-10. The morphology code describes the characteristics of the tumour itself, including its cell type and biologic activity. The alphabetical index gives codes for both topography and morphology and includes selected tumour-like lesions and conditions. A guide to differences in morphology codes between the second and third editions is provided in the final section, which includes lists of all new code numbers, new terms and synonyms added to existing code definitions, terms that changed morphology codes, terms for conditions now considered malignant, deleted terms, and terms that changed behaviour codes.