The Everton contracted striker suffered a serious knee injury during Besiktas’ 4-2 win away at Erzurumspor in the Turkish Super Lig on Sunday.
He had to be stretchered off the pitch and was taken to hospital, with his season believed to be over.
According to Turkish broadcaster TRT Spor, Tosun has now undergone surgery on his knee and an announcement is expected later today from Besiktas.
The striker is likely to head back to parent club Everton, with his loan at Besiktas effectively over.
Tosun, 29, made just five Premier League appearances for Everton, along with turning out in the EFL Cup and FA Cup, before being loaned to Besiktas in January.
He remains a firm favourite at the Turkish giants, where he has scored 67 goals in a total of 146 games.
Tosun will be hoping to recover as soon as possible in order to get his career back on track.
