ERBB3 and schwannoma: As PI3K/AKT activation occurs through ErbB3 and MET (77), which, as mentioned above, was upregulated in our series, we suggest that SPP1 upregulation, in addition to the mutations of the NF2 gene and 22q LOH, may lead to the complete absence of the merlin protein in schwannomas, even in samples with no hits in the NF2 gene and taking into consideration that epigenetic inactivation of this gene seems to be a rare event in schwannomas (17–21).