New Borussia Dortmund signing Sebastien Haller has left their training camp after a tumor was discovered in his testicle, the Bundesliga club said on Monday.
The 28-year-old Ivory Coast international travelled back to Dortmund to undergo medical tests after feeling unwell.
"This news today came as a shock to Sebastien Haller and to all of us," said BVB sporting director Sebastian Kehl.
"We will do everything in our power to ensure that he receives the best possible treatment."
The club said Haller will be absent for an indefinite period.
Haller joined Dortmund from Dutch side Ajax Amsterdam on a four-year contract earlier this month.