RPS6 and brain neoplasm: In summary, we here present pitfalls and provide a recommendation for immunohistochemical assessment of mTORC1 signaling using phospho-specific antibodies against phospho-RPS6 (Ser235/236), phospho-RPS6 (Ser240/244), phospho-4EBP1 (Thr37/46) in routine FFPE brain tumor specimens.