Sol, 25, discovered the tumour before Willem’s KNVB Beker clash against Heerenveen in midweek, but decided to play instead and told his team-mates afterwards.
The forward scored to help Willem secure a 2-1 victory on the night before successfully undergoing an operation on Thursday.
And Willem fans came together to pay a touching tribute to Sol during their clash against Ajax on Saturday, with several supporters holding up Spanish flags in his honour.
Willem were beaten 3-1 by Ajax after the Dutch giants produced a late fightback at the Koning Willem II Stadion.
Etien Velikonja gave the hosts the lead from the penalty spot after 55 minutes before Lasse Schone levelled things 15 minutes later.
Siem de Jong then fired Ajax in front after 79 minutes before David Neres wrapped up the victory with a late strike.
