What is Chapter 02 of ICD-11?
The Chapter 02 of the ICD-11 groups the neoplasms. The official guide explains that its general hierarchy is organized by tumor behavior, then by site or system wide, then by specific site and finally for morphological or histological type. This structure represents one of the most important changes compared to ICD-10, because it adds greater histopathological detail within the main tumor sites.
The WHO also indicates three relevant exceptions to this general hierarchy: neoplasms of the brain and central nervous system, neoplasms of the hematopoietic and lymphoid tissues and the malignant mesenchymal neoplasms, which follow their own logic within the chapter.
The reference guide itself justifies this reorganization by pointing out that a categorization based only on the anatomical location of the tumor provides limited information for prevention, treatment and prognosis. Therefore ICD-11 introduces finer subdivisions into major tumor sites and maintains special groups for tumors of the central nervous system, hematolymphoid neoplasms, and malignant mesenchymal neoplasms.
General structure of Chapter 02
According to the WHO, the general hierarchy of chapter 02 is organized as follows:
- 1st level: tumor behavior
- 2nd level: large sites or systems
- 3rd level: specific site
- 4th level: morphological or histological type
Main blocks of Chapter 02
This chapter is better understood if you read it first behavior and then by anatomical groups. Here you have a practical version, with main blocks and representative examples.
They constitute the main core of the chapter. ICD-11 maintains broad anatomical axes, but adds more histopathological subdivisions. The guide especially highlights tumors of the central nervous system and hematolymphoid neoplasms as groups with their own logic.
| Code | Diagnosis or representative group |
|---|---|
| 2A00 | Primary neoplasms of brain |
| 2B90.Z | Malignant neoplasms of colon, unspecified |
| 2C.. | Primary malignancies of other systems and specific sites |
They group secondary malignant neoplasms. The guideline dedicates specific instructions to differentiating primary and secondary tumors, and highlights a list of common sites of metastasis such as brain, liver, bone, pleura, lung, and lymph nodes.
| Code | Diagnosis or representative group |
|---|---|
| 2D70 | Malignant neoplasm metastasis in lung |
| 2D80.0 | Malignant neoplasm metastasis in liver |
| 2D.. | Metastasis and secondary dissemination by site |
Tumor behavior remains a centerpiece of the chapter. The official guide differentiates malignant neoplasms, in situ, benign, uncertain behavior, and unknown behavior. This distinction is key when the clinical report does not make clear the actual behavior of the tumor.
| Code | Representative group |
|---|---|
| 2F00–2F4Z | Neoplasms in situ |
| 2F50–2F8Z | Benign neoplasms |
| 2F90–2F9Z | Neoplasms of uncertain or unknown behavior |
These codes are used when the documentation does not allow us to conclude whether the neoplasm is malignant, benign, or another behavior. The guide gives clear examples with colon, bladder, lung and breast when the behavior is not specified in the certificate.
| Code | Diagnosis or representative group |
|---|---|
| 2F90.0 | Neoplasms of unknown behaviour of colon |
| 2F91.1 | Neoplasms of unknown behaviour of trachea, bronchus or lung |
| 2F95 | Neoplasms of unknown behaviour of breast |
| 2F98 | Neoplasms of unknown behaviour of urinary organs |
The official guideline notes that central nervous system tumors were removed from the basic behavioral framework because the histological and behavioral distinction between benign and malignant can be a “gray area.” That is why they are grouped following a special logic within the chapter.
| Code | Representative example |
|---|---|
| 2A00 | Primary neoplasms of brain |
Another special group of the chapter. According to the guide, the hierarchy here is organized first by broad histological type and then by specific subtype, rather than prioritizing anatomical site.
| Hierarchy | Description |
|---|---|
| 1st level | Broad morphological or histological type |
| 2nd level | Specific morphological or histological type |
The guideline also identifies malignant mesenchymal neoplasms as an exception to the general hierarchy. In this case, classification prioritizes the specific histological subtype first and then the site.
| Hierarchy | Description |
|---|---|
| 1st level | Specific histological type |
| 2nd level | anatomical site |
Comparison ICD-10 vs ICD-11 — Chapter 02
Main structural differences according to the official WHO Reference Guide:
| ICD-10 block | Equivalent or change in ICD-11 |
|---|---|
| C00–C97 Malignant neoplasms | 2A00–2E9Z with greater histopathological detail and better distinction between primary and secondary |
| D00–D09 Neoplasms in situ | 2F00–2F4Z Neoplasms in situ |
| D10–D36 Benign neoplasms | 2F50–2F8Z Benign neoplasms |
| D37–D48 Uncertain or unknown behavior | 2F90–2F9Z Uncertain or unknown behavior |
| CNS tumors mixed by behavior and site | Special group for the “gray zone” between benignity and malignancy |
| Less histological detail in many sites | Expanded histopathological subdivisions in main tumor locations |
Coding Guidance
1. Tumor behavior
The guide insists on first defining whether the neoplasm is malignant, on site, benign, uncertain or unknown. That is the starting point of the classification in this chapter.
2. Primary or secondary?
If the neoplasm is malignant, the next step is to decide if it is a neoplasm primary or secondary. The guide includes specific instructions for interpreting terms such as “primary,” “originated from,” “secondary,” “metastatic,” or “unknown primary site.”
3. “Metastatic” cancer
The guideline cautions that a neoplasm described as “metastatic” may refer to a primary tumor that has metastasized or to a secondary malignancy. That is why it is not advisable to automatically assume one or the other without reviewing the clinical context.
4. Unknown primary site
If the report does not allow the primary site or behavior to be identified with certainty, ICD-11 provides categories of unknown behavior or primary site not clearly indicated. This point is relevant in death certificates and incomplete records.