Before my diagnosis in February 2019, no one in my family had ever had cancer. So we were all very surprised when I was diagnosed with triple-negative invasive ductal carcinoma — a form of breast cancer — at age 27.

It turns out that I inherited a genetic mutation called BRCA1 from my father. He was adopted, so we didn’t know anything about his biological parents.

The bad news is the BRCA1 mutation makes it more likely that...