# What is TNM cancer staging, and what do stages 1 to 4 mean?

Source: https://oncologyistanbul.com/answers/what-does-tnm-staging-mean
Last updated: 2026-07-12

According to the U.S. National Cancer Institute (NCI), the TNM system is the staging system used most often for cancer. It captures three pieces of information: T refers to the size and extent of the main (primary) tumor; N refers to the number of nearby lymph nodes that have cancer; and M refers to whether the cancer has metastasized. Doctors combine the T, N, and M results to assign an overall stage. NCI notes many cancers are also grouped into stages 0 and I-IV. Stage 0 means abnormal cells are present but have not spread to nearby tissue (carcinoma in situ). For stages I-III, higher numbers mean a larger tumor that has spread more into nearby tissues, and stage IV means the cancer has spread to distant parts of the body. This is general information, not personal medical advice.

## Verify at
- [Cancer Staging (TNM system)](https://www.cancer.gov/about-cancer/diagnosis-staging/staging) — National Cancer Institute (NCI) (checked 2026-07-12)

Related: [TNM staging, defined in the glossary](https://oncologyistanbul.com/glossary/tnm-staging)