The 2026 Solid Tumor Rules and change logs are now available on the SEER website: https://seer.cancer.gov/tools/solidtumor/.
Changes implemented this year include
- Restructured general instructions
- Reformatted and restructured the histology tables
- Changed from 3 columns to 2 columns
- Histology corrections made in several site-group tables
- Updated instructions about ambiguous terms for determining histology
- Breast rules M10 and H28 deleted
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.
Alison L. Van Dyke, MD, PhD, MPA, FCAP
Medical Officer - Research
Data Quality, Analysis, and Interpretation Branch
Surveillance Research Program
Division of Cancer Control and Population Sciences
National Cancer Institute
National Institutes of Health
9609 Medical Center Drive, 4E348 MSC 9763
Rockville, MD 20850
Office Phone: 240-276-6039
Email: alison.vandyke@nih.gov