Presently, genetic aberrations reported in PCNSL include CARD11, CD79B, CDKN2A (9p21; p16), ETV6, MYD88, PIM1, PRDM1, TBL1XR1, TNFAIP3(A20), and TOX.[9,16] Half of the selected genes are involved in the NFκB pathway (CARD11, CD79B, MYD88, TBL1XR1, and TNFAIP3), while the other half is not (CDKN2A, ETV6, PIM1, PRDM1, and TOX).[9] Unfortunately, none of these genetic aberrations were detected in this patient. The gene discussed is TOX; the disease is primary central nervous system lymphoma.