Football Insider first reported that Mavropanos has his "heart set" on a return to the Bundesliga following three years at the London Stadium, with Champions League football the primary draw.
Sky Sport Germany's Florian Plettenberg confirmed that Dortmund had held internal discussions about signing the 28-year-old Greece international, describing his interest in the move as genuine and specific.
However, Bild has since reported that Dortmund are having second thoughts after learning of West Ham's minimum asking price of €30 million — a figure Dortmund regard as too high for a player who turns 29 in December and whose market value is assessed significantly lower by most external sources.
West Ham's position is firm. With Mavropanos under contract until 2028, the club holds the leverage and have confirmed internally they are "calm" about the speculation, viewing it as standard practice ahead of contract renewal talks.
Mavropanos has made 30 appearances this season, scoring three goals, and has been one of the few consistent performers during the club's relegation battle. Other Premier League clubs are also monitoring the situation, meaning Dortmund are not the only option available to the player if a cross-border deal cannot be agreed.