Stage Groups

For staging purposes, three different areas are evaluated

  • Primary tumor (extent of disease)
  • Regional lymph nodes
  • Metastatic disease

The combination of primary tumor, regional lymph nodes, and metastatic disease, form stage groups that are used to determine prognosis, treatments, and outcomes. These stage groups are based on the TNM system that has been used internationally for many years. As clinical medicine continues to evolve, staging criteria and definitions continue to change.

For SEER, this information is collected in the following

  • EOD Primary Tumor
  • EOD Regional Nodes
  • EOD Mets

Note 1: The US follows the American Joint Committee on Cancer (AJCC) for the TNM chapters and definitions.

Note 2: SEER does not collect AJCC staging (and therefore does provide training on AJCC). AJCC is a clinical, pathological, and post-therapy staging system. SEER collects combined clinical and pathological staging, resulting in the most complete evaluation of the primary tumor, regional lymph nodes, and metastatic disease. Also, unlike AJCC/CoC, EOD applies to and is collected by SEER for all cases in their SEER registries (population based).

Updated: June 24, 2025