Castaignos only joined Inter Milan from Dutch giants Feyenoord 12 months ago, but he has failed to make the expected impact at the Italian side.
The 19-year-old has recently been linked with Liverpool and West Ham United.
“Inter wants to loan me to an Italian club or sell me,” Castaignos said to Sky Italia. “I told them that I don’t want to play anywhere else in Italy but at Inter.
“I came to Italy to wear the Nerazzurri colours and not play for any other club. Now I must go and Inter will help me find a club.
“I am saddened, I cannot deny it, I am disappointed not to have shown my worth, but this is football.
“It’s a decision taken by the club and by me. Now I want to join a big club.”