TOKYO—Sam Grewe made a choice when he was 13 to have his right leg amputated after he was diagnosed with an aggressive bone cancer. He could have chosen to keep the leg, but he said it would have been a frail limb once surgeons carved out the “fist-size tumor.” That procedure also would have ruled out any sports for life. “There’s no doubt in my mind that I made the right decision,” the American said Tuesday after taking gold in the high jump in the T64 class at the Paralympics. Grewe said he thought at the time about still wanting to be an athlete. “I want to lose my leg if that’s what it takes,” he recalled. His winning jump Tuesday of 1.88 meters was just under the world record he holds for the class at 1.90 (6 feet, 2 3/4 inches). He beat silver medalist Mariyappan Thangavelu of India, …