MTOR and neoplasm: For example, using molecular profiling of paired brain metastases and corresponding primary breast tumors by whole-exome sequencing, Brastianos et al., showed that brain metastases exhibit genomic aberrations in the cyclin-dependent kinase (CDK) pathway and phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin (PI3K/AKT/mTOR) pathway; however, many of these alterations were not detected in the corresponding primary tumor [38].