Plotting of cumulative insertion patterns for five distinct families of CIS genes (Wnt, Fgf/Egf, Fgfr, Rspo and Pdgfr) revealed a typical mutually exclusive integration pattern for genes within each family (Figure 4), showing that MMTV infected cells gain little to no selective advantage from MMTV insertions near multiple members of the same gene family. The gene discussed is EGF; the disease is in situ carcinoma.