The most common molecular alterations in PCNSL include mutations (MYD88 and CD79) and CDKN2A homozygous deletion.11 In addition, CN losses in 6p21 (HLA-D locus) as well as recurrent losses in 9p21 (MTAP, CDKN2A/B) and 19p13 (CDKN2D) are more common in comparison to DLBCL.12 We sought to assess the effect of CDKN2A homozygous deletion on sensitivity to induction chemotherapy. The gene discussed is MTAP; the disease is diffuse large B-cell lymphoma.