We also reported that MBCs frequently harbored mutations in the Wnt pathway.9 Consistent with our observations from whole-exome sequencing analysis of MBCs,9 we did not identify expressed mutations affecting CTNNB1. We did, however, detect an expressed frameshift SMAD4 mutation and an expressed missense TCF7L2 mutation. The gene discussed is TCF7L2; the disease is maternal uniparental disomy of chromosome 20.