ICDO4 for consultation

International Classification of Diseases, 4^th Edition (ICD-O-4)

As you might be aware, following completion of the 5^th Edition of WHO Classification of Tumours (Blue Books), the ICD-O-3.2 classification was updated with new morphology codes and terms.

We are now moving forward with ICD-O-4, the fourth edition of the ICD-O classification which has a new morphology structure containing 5-digit codes, in which the fifth digit can be “0” or have other values (including alphanumeric), if more specific codes are needed. The structure has evolved to enable the assigning of specific codes to each separate cancer entity that were previously included as related terms. ICD-O-4 also contains an updated topography list.

The new ICD-O-4 online version, will become available in Spring 2025.

Alongside the ICD-O-4 morphology and topography list, we are now providing draft listings of additions, changes, and revisions between ICD-O-3.2 and ICD-O-4 as reference material for cancer registries in the following tables:

1. New morphology codes:
   3. First 4 digits present in ICD-O-3.2 and 5^th digit different from “0”
   4. First 4 digits present in ICD-O-4, but not in ICD-O-3.2
2. Changes between ICD-O-3.2 and ICD-O-4:
   1. Morphology at the 4-digit level
   2. Topography

Please provide any comments or queries using the feedback function (contact form). The site is open for feedback until the 1st of November 2024. After the consultation period, ICD-O-4 will be reviewed, and the book generated as an online pdf.