Sebastien Haller made his first appearance for Borussia Dortmund on Tuesday, less than six months after starting treatment for testicular cancer.
The Ivory Coast striker arrived from Ajax in July but was almost immediately sidelined after the discovery of a malignant tumour during pre-season testing in July.
Haller underwent two surgeries and chemotherapy, and was present as Dortmund returned to training for the first time after the World Cup last week at a camp in Marbella, Spain.
In the 74th minute of Dortmund's 5-1 friendly win against fellow German side Fortuna Dusseldorf, Haller replaced Youssoufa Moukoko to make his first appearance for the club, sharing a hug with head coach Edin Terzic before entering the pitch.
Terzic's side took an early lead when Felix Passlack finished from a neat throughball by Marco Reus, though Dusseldorf equalised almost immediately via a Dawid Kownacki penalty.
Jude Bellingham dribbled into the box to set up Karim Adeyemi for a simple second for Dortmund just after the half-hour mark, but they had to wait until after Haller's arrival to add further goals.
Nico Schlotterbeck swept home a Julian Brandt cross from the left with nine minutes to go, before Donyell Malen raced onto Thomas Meunier's ball over the top to make it four, and the Dutchman added a fifth just before full-time with a finish into the far-right corner following a delightful jinking run from the left.
Dortmund resume their Bundesliga campaign at home to Augsburg on January 22, having finished the first part of the season before the World Cup in sixth place, nine points behind leaders Bayern Munich.