The Belgium international left Ajax for Spurs over eight years ago.
"It is often asked if it could happen. It depends on so many factors," he told Ziggo Sports.
"Fitness-wise, what do I want, what does the club want with me ... But it will always be an option."
Dutch hero Wim Kieft says: "Those are gains for Dutch football. Jan has to decide for himself, but I would applaud it."