This edition of ICD-O, the standard tool for coding diagnoses of neoplasms in tumour and cancer registrars and in pathology laboratories, has been developed by a working party convened by the International Agency for Research on Cancer / WHO. ICD-O is a dual classification with coding systems for both topography and morphology. The book has five main sections. The first provides general instructions for using the coding systems and gives rules for their implementation in tumour registries and pathology laboratories. Section two includes the numerical list of topography codes, which remain unchanged from the previous edition. The numerical list of morphology codes is presented in the next section, which introduces several new terms and includes considerable revisions of the non-Hodgkin lymphoma and leukaemia sections, based on the WHO Classification of Hematopoietic and Lympoid Diseases. The five-digit morphology codes allow identification of a tumour or cell type by histology, behaviour, and grade. Revisions in the morphology section were made in consultation with a large number of experts and were finalised after field-testing in cancer registries around the world. 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 code, terms for conditions now considered malignant, deleted terms, and terms that changed behaviour code.

"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 tumor 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 tumor itself, including its cell type and biologic activity.In preparing this revised edition, the editors have made a special effort to change as few terms as possible, to add new terms at empty spaces, and to avoid reuse of previously assigned codes. While all topography codes remain the same as in the previous edition, morphology codes have been thoroughly reviewed and, where necessary, revised to increase their diagnostic precision and prognostic value.

Epidemiologists, statisticians, oncologists as well as tumor registrars are interested in studying trends in both incidence and mortality. To be able to compare data from one period to another, it is essential that conversion tables be available so that all data is on the same code. The following conversion (comparison or equivalency) tables are from ICD-O-2 and back to the Field Trial editions and ICD-O-1. These tables are divided into Topography and Morphology. There is only one conversion table for the topography since ICD-O-1 and the Field Trials used the same Topography section. There is also one table for Morphology but with three columns: two for the Field Trials, 1988 and 1986 and one for ICD-O-1. The 1987 Field Trial was exactly the same as the 1988 Field Trial except for three terms in Hodgkin's disease: 9657, 9658 and 9659. In all probability this conversion will not be done on records, although a program on tape will be made on request. This conversion is made to help users see what the equivalent code number(s) was in a Field Trial or ICD-O-1.

Epidemiologists, statisticians, oncologists as well as tumor registrars are interested in studying trends in both incidence and mortality. To be able to compare data from one period to another, it is essential that conversion tables be available. The following conversion (comparison or equivalency) tables are from ICD-O-1 and the Field Trial editions to ICD-0-2. These tables are divided into Topography and Morphology. There is only one conversion table for the topography since ICD-O-1 and the Field Trials used the same Topography section. However there are three tables for Morphology: one for ICD-O-1, one for the Field Trials, and one for special codes introduced by the Surveillance, Epidemiology, and End Results Program (SEER) of the National Cancer Institute (NCI).