Solid Tumor Rules

For Colorectal cancers multiple primary determination focuses on tumors in the multiple subsites. When there are multiple tumors, it is important to carefully read the Solid Tumor Rules to determine how many primaries should be abstracted.

The Colon Solid Tumor Rules should also be used to assign histology for colon and rectal primaries. Some tumors may have more than one histology present, and the rules will direct you to the appropriate histology code.

Solid Tumor Rules. Colon, Rectosigmoid, and Rectum Histology Rules

Updated: June 24, 2025