RB1 and primary central nervous system lymphoma: While TP53 alterations seem to play a minor role in PCNSL, the CDKN2A/B genes encode several proteins that regulate either the p53 (p19 ARF) or the RB1 (p16 INK4a) pathway147,148, underlining the relevance of the TP53 pathway in the context of PCNSL and cell cycle control.