We were surprised, but it happens. Breast cancer can be very fast moving.
Unless they have family history, women aren't told to do annual exams until you hit 40.
The symptoms may not be too specific or startling even when it is into stages 3 & 4.
Worth reminding the women in your lives to check their family history and consider getting early exams either way. A lot of times it turns out women do have family history that went undiscussed until they ask mom, aunts, grandmothers, etc.
The other cancers that worry me are the slow moving imperceptible symptomless ones like pancreatic, liver, kidney, etc. Know a few people who around 50 discovered they had stage 2-3 cases due to unrelated scans they got from an accident injury. Some of these you have 5-10+ years window to treat it and live without impact to lifespan.. but most people don't catch it until stage 4 when they actually feel sick and it is too late.
Some people die by cancer, other overcome the cancer, and a small amount don't stand the treatment and die by the chemotherapy. Sometimes by genetics, and can't always be known before. It also depends on how much advanced and aggressive is the tumor.
