Importantly, as in BCP-ALL [19], also T-ALL samples at relapse showed a median value of CRLF2 expression higher than the respective samples at diagnosis, this might indicate that blasts with high level of CRLF2, already present at diagnosis in various percentage, are associated with a higher resistance to therapy and are positive selected at relapse or that CRLF2 expression is gained during treatment. The gene discussed is CRLF2; the disease is acute lymphoblastic leukemia.