My mother was diagnosed with breast cancer when she was 94. My mother-in-law had it when she was in her 40s. But to my knowledge, there’s no history of brain cancer in our family.

So, when my son, Eric, was diagnosed with pineal germinoma — a type of childhood germ cell tumor — in his brain in August 2021, I was stunned. He was only 24 at the time and had just started his dream job as the new percussion director at a Houston-area...