Lewandowski scored all four goals as Dortmund thrashed Real Madrid 4-1 in the first leg of their Champions League semi-final on Wednesday but much of the post-match talk centred around his future.
His contract expires at the end of next season, leaving Dortmund in the unenviable position of having to decide whether to cash in this summer of risk seeing the 24-year-old leave on a free in 2014.
Reports in Germany suggest they have opted for the former, with the player's agent Maik Barthel suggesting Dortmund have sanctioned his departure.
"We have reached an agreement with a club and intend (him) to move this summer," Barthel told Sport Bild.
"There is a very interesting offer for Robert which fulfils entirely the demands set by Dortmund and also the demands of Robert.
"Dortmund have assured us that Robert can move at the end of the season under these conditions.
"We stick to agreements and now it's up to the clubs to sort things out."
Barthel stopped short of naming the club in question but speculation suggests it is Bayern Munich, who earlier this week agreed to activate the 37 million euros release clause of Dortmund playmaker Mario Gotze.
Losing two of their best players to their closest domestic rivals would be a major setback for Dortmund, who are also likely to meet Bayern in the Champions League final at Wembley after the Bavarians' 4-0 hammering of Barcelona on Tuesday night.