BL is a very aggressive tumor characterized by a monotonous proliferation of medium-sized tumor cells, often associated with a “starry sky” pattern, GCB phenotype (CD10+, BCL6+, BCL2−), high proliferative index (Ki67 > 90%), IG::MYC juxtaposition and mutations involving TCF3 (E2A) or its repressor ID3 [154]. The gene discussed is MKI67; the disease is Burkitt lymphoma.