YAP1 and neoplastic disease or syndrome: YAP1 (Yes-associated protein 1) and its paralog transcriptional coactivator with PDZ-binding motif, Tafazzin (TAZ), which are the principal effectors of the Hippo signaling pathway, are relatively inactive in adults to maintain organ homeostasis, while they are robustly induced during neoplastic disorders [1,2,3].