ESR1 and mantle cell lymphoma: Beyond ER+ breast cancer, promising activity of CDK4/6 inhibitors in mantle cell lymphoma (MCL), liposarcoma, melanoma, non-small cell lung cancer (NSCLC), glioblastoma, neuroblastoma and malignant rhabdoid tumors has been shown (Leonard et al., 2012; Dickson et al., 2016; Patnaik et al., 2016; Geoerger et al., 2017).