For example, FGFR3 mutations are not found in CIS (carcinoma in situ) but they coexist with TP53 mutations in 10–20% of invasive BCs as do deletions of both chromosome 9 (typical of low-grade disease) and 17p (locus of TP53) in 15–74% BC 4,8. The gene discussed is FGFR3; the disease is in situ carcinoma.