Testicular cancer is the most common solid malignancy among males aged 15 to 40 years in the US, with approximately 10,000 new cases diagnosed each year. Between 90% and 95% of testicular cancers are germ cell tumors (GCTs). This JAMA review summarizes current evidence regarding risk factors, diagnosis, and treatment of testicular cancer in adults and adolescents. Learn more: ja.ma/42BMCsW