ICD-O-3 — International Classification of Diseases for Oncology, 3rd Edition

Overview

ICD-O-3 is a dual-axis classification for coding tumours in cancer registries, developed by the WHO and the International Agency for Research on Cancer (IARC). First published in 2000 and currently in its third revision (ICD-O-3.2, 2019), it classifies every tumour along two independent axes: topography (anatomical site of origin) and morphology (histological type, behaviour, and grade). A fourth edition (ICD-O-4) is in development by IARC, harmonised with ICD-11.

Two-Axis Structure

• Topography axis codes the anatomical site of origin (C00–C80), using the same site codes as ICD-10’s neoplasm chapter but extended to cover all tumour types including benign and in situ.
• Morphology axis codes the histological type and biological behaviour of the tumour. Behaviour is encoded as a single digit suffix: benign (/0), uncertain (/1), in situ (/2), malignant primary (/3), or malignant metastatic (/6).

Connections

• Published by: WHO / IARC
• Required by: OSIRIS (French oncology data model)
• Maps to: ICD-10 (shared topography codes)

Resources

• https://www.who.int/standards/classifications/other-classifications/international-classification-of-diseases-for-oncology (WHO page)
• https://www.iarc.who.int/tools-and-services/tools/icd-o-3/ (IARC ICD-O-3 page)
• https://apps.who.int/iris/handle/10665/42344 (ICD-O-3 manual PDF)
• https://www.sciencedirect.com/science/article/abs/pii/S1877782126000044 (ICD-O-4 overview, 2026)