NOTCH1 and mantle cell lymphoma: Gain-of-function mutations of NOTCH1 are common in T lymphoblastic leukemia/lymphoma (T-LL) [2,3], and have also been described in subsets of chronic lymphocytic leukemia (CLL) [4–6], mantle cell lymphoma (MCL) [7], diffuse large B cell lymphoma [8], peripheral T cell lymphoma (PTCL) [9], breast cancer [10], and non-small cell lung cancer (NSCLC) [11].