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Purpose of Solid Tumor Rules
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.
2026.1 Solid Tumor Rules Release Announcement
The Solid Tumor Rules have been updated for release on July 20, 2026 (2026.1 Update).
Key updates include the following:
- Alignment of histology tables with Cancer PathCHART
- Clarified that patterns of lung adenocarcinoma are able to be used for mixed subtypes (8255/3)
- Deleted inaccurate note that stated 8010/2 is impossible for lung
- Changed coding instructions for ductal adenocarcinoma (8500/3) for prostate
- Changed reportability instructions for paragangliomas: all are reportable as /3 behavior even if stated to be benign
- Clarified reportability instructions for gastrointestinal stromal tumors (GISTs): all are reportable as /3 behavior even if stated to be benign, borderline, or NOS
See the Revision History for a comprehensive description of changes.
NOTE: For information on implementation of the 2026 update, see the Diagnosis Years for Which the Solid Tumor Rules Should Be Used section in the General Instructions (page 7).
Educational Opportunities
- What Is New and Different in the Solid Tumor Rules 2026.1 Update?
- Solid Tumor Rules Registrar Education Series: Ambiguous and Definitive Terms for Determining Histology in the Solid Tumor Rules 2026 Update
- The 2026 updates to the Solid Tumor Manual were discussed during the V26 Updates: Solid Tumor Rules, SSDIs, CPC and More informational webinar on January 14, 2026.
Where Should I Submit Questions?
Questions concerning the Solid Tumor Rules Manual can be directed to the Ask A SEER Registrar Forum.
Revision History
Significant formatting changes were made to the histology tables. Please see the 2026 Update Revisions. Changes for earlier versions are available in the Revision Archive.
Suggested Citation
Dickie, L., Adams, S., Harrison, D., Hofferkamp, J., Traverso-Ortiz, M., Van Dyke, A., Negoita, S. (December 2025). Solid Tumor Rules. National Cancer Institute, Rockville, MD 20850.
