Borussia Dortmund striker Sebastien Haller has withdrawn from their pre-season camp in Switzerland after discovering a tumour, the club has confirmed.
The Ivory Coast international, who signed for the Black and Yellow on a four-year deal earlier this month from Ajax, has returned to Germany for further tests.
The Bundesliga outfit asked for the privacy of the 28-year-old and his family to be respected, adding they would provide further updates when possible.
Haller initially complained of feeling unwell after a training session on Monday, before subsequent medical examinations discovered a tumour on his testicle.
"This news today came as a shock to Sebastien Haller and to all of us," sporting director Sebastian Kehl stated.
"The entire BVB family wishes Sebastien a full recovery as soon as possible and that we can hug him again soon. We will do everything in our power to ensure that he receives the best possible treatment."
Haller's move to Dortmund marks his second Bundesliga spell, after previously playing for Eintracht Frankfurt, and comes on the back of an impressive resurgence at Ajax following a lacklustre period with West Ham.
The forward finished last season as the Eredivisie's top scorer, with 21 goals in 31 games.