Coding CS Tumor Extension
Important
These modules are archived and should only be referenced for historical purposes.
CS Extension identifies contiguous growth of the primary tumor within the organ or direct extension into neighboring organs. For two sites, ovary and corpus uteri, discontinuous metastasis is coded in the CS extension field. Site-specific schemes contain detailed codes and coding instructions.
CS Tumor Extension allows the data to be collapsed into the AJCC T component and Stage Group, Summary Stage 1977, and Summary Stage 2000 (localized or regional direct extension), and provides flexibility for consistency over time.
Illustration showing an example of coding tumor extension codes 40-55.
View the General Rules for Coding Tumor Extension.
Suggested Citation
SEER Training Modules: Coding CS Tumor Extension. U.S. National Institutes of Health, National Cancer Institute. Cited 19 December 2025. Available from: https://training.seer.cancer.gov.