Guido Lindken is in his early 50s, a married family man and travels a lot as a sales representative. In his free time, he is active in sports, plays tennis and soccer and meets up with friends. In March 2021, he notices that he finds it harder to breathe and starts sweating quickly even with minor exertion. For no apparent reason, his fitness has declined significantly. When the swelling of the lymph nodes on the left side of his neck persists for weeks and a foreign body-like sensation when swallowing does not go away, he visits an ENT practice.