> ## Documentation Index
> Fetch the complete documentation index at: https://docs.corti.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# ICD-O-3

> International Classification of Diseases for Oncology, 3rd Edition. The WHO standard for cancer registry coding

**ICD-O-3 is a dual-axis code system for oncology, published by the World Health Organization.** It is used worldwide by cancer registries to code every recorded tumor with a topography code (the anatomical site) and a morphology code (the histological type and behavior).

## Overview

* Around 1,600 codes across two axes: topography (C-codes, e.g., `C18.2`) and morphology (M-codes, e.g., `8480/3`).
* Each tumor is coded with a paired topography and morphology code, and the two axes are searched and reconciled together.
* Morphology codes carry a behavior suffix that indicates how the tumor is expected to act: `/0` benign, `/1` uncertain, `/2` in situ, `/3` malignant, `/6` metastatic, `/9` uncertain whether a primary or metastatic site.

## Editions

| Edition | Language | System identifier | Status |
| :- | :- | :- | :-: |
| [ICD-O-3](https://docs.corti.ai/coding/icd-o-3-int.md) | English (International) | `icdo3int` | Available |
| [ICD-O-3](https://docs.corti.ai/coding/icd-o-3-de.md) | German | `icdo3de` | Available |
| [ICD-O-3](https://docs.corti.ai/coding/icd-o-3-fr.md) | French | `icdo3fr` | Available |

The `system` field accepts the edition identifier. ICD-O-3 does not use an encounter-type suffix.

## Morphology behavior

Morphology codes carry a behavior suffix that indicates how the tumor is expected to act. The suffix is the digit after the slash, for example the `/3` in `8480/3`.

| Suffix | Behavior |
| :-: | :- |
| `/0` | Benign |
| `/1` | Uncertain whether benign or malignant |
| `/2` | In situ |
| `/3` | Malignant, primary site |
| `/6` | Metastatic |
| `/9` | Uncertain whether primary or metastatic |


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