Borussia Dortmund striker Sebastien Haller is to undergo chemotherapy for a testicular tumour and is expected to be out for several months.

The Ivory Coast forward, 28, was was diagnosed earlier this month after complaining that he felt unwell.

Earlier this week the club reported he had successfully undergone surgery.

"Sebastien will now receive the best possible treatment, the chances of recovery are very good," said Dortmund sporting director Sebastian Kehl.

Former West Ham striker Haller signed a four-year deal with the Bundesliga side after moving from Ajax for 31m euros this month.

The club said: "Sebastien Haller (28) will be absent from Borussia Dortmund for several months. The histological findings revealed a malignant testicular tumour. Haller therefore has to undergo chemotherapy treatment."