ASCL1 and atypical teratoid rhabdoid tumor: Protein expression of proneural marker Achaete-scute homolog 1 (ASCL1, also known as MASH1), a transcription factor [1] interacting with Notch signaling, has been proposed as a surrogate diagnostic marker for ATRT–SHH and has also been associated with improved outcome in ATRTs [40].