CREB binding protein (CREBBP) is considered to be an epigenetic regulator with diverse functions that include acetyltransferase activity, scaffolding function for transcription factor complexes and ubiquitin ligase activity. CREBBP mutations may occur as germline variants in Rubinstein Taybi syndrome and as somatic variants where they have been described in lymphoid malignancies. Missense, frameshift and nonsense mutations of CREBBP have been reported in 13-43% of B cell acute lymphoblastic leukemia and tend to occur in the HAT domain that is encoded by exons 18 through 29; more specifically, the missense mutations typically cluster in exons 25-27 of the HAT domain, however, mutations in other regions in the protein have been reported and may be important. CREBBP mutations have also been described in diffuse large B cell lymphoma and follicular lymphoma. Deletions/loss of heterozygosity of CREBBP has been described in ALL but are not detectable by this assay. Mutations of CREBBP appear to predominate in hyperdiploid B cell ALL, especially in such cases associated with disease relapse.