The present invention relates to 4-(4-Fluoro-2-methoxyphenyl)-N-{3-[(S-methylsulfonimidoyl)methyl]phenyl}-1,3,5-triazin-2-amine (compound A), more particularly (+)-4-(4-Fluoro-2-methoxyphenyl)-N-{3-[(S-methylsulfonimidoyl)methyl]phenyl}-1,3,5-triazin-2-amine (compound A′), for use in treating lymphoma, preferably diffuse large B-cell lymphoma (DLBCL) mantle cell lymphoma, follicular lymphoma, diffuse large B-cell lymBurkitts lymphoma, adult T-cell lymphoma (ATL) and Hodgkins lymphoma, more preferably DLBCL and ATL.