Complex sentence: Interestingly, most cases of PIOL eventuate to central nervous system involvement (PCNSL) while only 20% of PCNSL lead to intraocular (PIOL) involvement.
Split into simpler sentences: Interestingly, most cases of PIOL eventuate to central nervous system involvement (PCNSL). However, only 20% of PCNSL lead to intraocular (PIOL) involvement.