The purpose of the Solid Tumor Rules is to determine the number of primaries to abstract and the histology to code. The most recent Solid Tumor Rules update should be used as soon as it is released and can be applied to 2018+ cases (see General Instructions for start years for each Site Group). If a specific code or instruction has an effective year later than 2018, it will be noted in the text.

The Solid Tumor Rules are revised annually to reflect new terminology, ICD-O codes, and other changes to keep in step with current clinical practice. It is important to review the current change log as it will provide helpful information on changes made to the annual update.

Beginning with the 2025 Solid Tumor Update, the rules will be available in a combined file only. Individual site-specific sections will no longer be provided.

Download the Solid Tumor Rules 2025 Update (PDF, 7.9 MB) (December 9, 2024)

Revision History

See change log for updates made in November 2024. Please see the Revision Archive for earlier changes.

Histology Coding Clarifications

On occasion, data collection requirements of AJCC and NCI SEER have resulted in conflicting cancer coding instructions for cancer registrars. For more information and specific instructions about reviewing cases already coded, please visit the Histology Coding Clarifications page.

Suggested Citation

Dickie L., Johnson, CH., Adams, S., Negoita, S. (November 2024). Solid Tumor Rules. National Cancer Institute, Rockville, MD 20850.