Intratumor heterogeneity has been shown to be prognostic in certain cancer types and can also explain the partial efficacy of targeted therapies (Andor et al., 2016; Landau et al., 2013; Rocco, 2015; Yates et al., 2015) or why it is impossible to achieve complete responses with BTK inhibitors as monotherapy in WM (Buske et al., 2022; Tam et al., 2020). Here, BTK is linked to cancer.