CTNNB1 and craniopharyngioma: Furthermore, ghost cells were present in two cases of ameloblastoma with BRAF and CTNNB1 mutations, indicating that ghost cells form due to mutations in CTNNB1. The data suggest that mutations in CTNNB1 are the major driver mutations of CCOT, and that CCOT is the genetic analog of pilomatrixoma and adamantinomatous craniopharyngioma in odontogenic tissue.