The Polish defender's representative has indicated that a move to Los Blancos would be a step forward in the player's career and refused to rule out a summer transfer
The 26-year-old has been suggested as a strong possibility to bolster Real Madrid's rearguard in the summer, as coach Jose Mourinho looks for reinforcements in defence.
Dortmund CEO Hans-Joachim Watzke said earlier in the week that Piszczek and compatriot Robert Lewandowski are not for sale, but the full-back's representative has seemingly declared that a transfer is possible.
"Lukasz is happy and Dortmund are a successful club, but Madrid are a worldwide legend," Bartlomiej Bolek told LaSexta.
"We will not make any comment about this, but whoever wants him will have to spend at least €10m."
Meanwhile, AS reports that Bolek has obtained Aitor Karanka's phone number and will contact the Madrid assistant coach to let him know that his client will jump at the chance to move to the Santiago Bernabeu.
Piszczek, who has 22 international caps to his name, has a contract until 2016 with Dortmund, whom he joined from Hertha Berlin in 2010.