More recently, our team has found that Myc is a key driver of the CSL phenotype in ALK+ALCL, and the differential expression of Myc proteins in ALK+ALCL cell lines generates intra-tumoral heterogeneity that can be detected as RU or RR cells by using a Sox2 reporter [38,39,40]. The gene discussed is ALK; the disease is anaplastic large cell lymphoma.