Scientists have created a detailed map that shows how hundreds of possible mutations in a major cancer gene, CTNNB1, drive tumor growth. By testing every possible mutation in a key part of this gene using mouse stem cells, the team measured how strongly each change triggered a pathway linked to cancer. Their experimental data matched genetic records from real patients, showing that cancers in different parts of the body tend to favor mutations that produce specific levels of activity. The findings also suggest that the strength of a mutation might change the number of immune cells inside a tumor, which could help doctors design more personalized treatments in the future.