My doctor didn’t notice anything unusual during my well-woman exam in February 2018. When I felt a lump in my breast two months later, I wasn’t overly concerned. I was only 38 years old. My husband said I should get checked again, but I didn’t think it would turn out to be breast cancer.

When I went to see my gynecologist a couple months later, my husband insisted that she re-examine me. My doctor ordered an ultrasound, a biopsy...