Reality: Roughly 70% of women diagnosed with breast cancer have no identifiable risk factors for the disease. But the family-history risks are these: If a first-degree relative (a parent, sibling, or child) has had or has breast cancer, your risk of developing the disease approximately doubles. Having two first-degree relatives with the disease increases your risk even more.
2. Myth: Wearing an underwire bra increases your risk of getting breast cancer.
3. Myth: Most breast lumps are cancerous.
Reality: Roughly 80% of lumps in women's breasts are caused by benign (noncancerous) changes, cysts, or other conditions. Doctors encourage women to report any changes at all, however, because catching breast cancer early is so beneficial. Your doctor may recommend a mammogram, ultrasound, or biopsy to determine whether a lump is cancerous.
4. Myth: Exposing a tumor to air during surgery causes cancer to spread.
Reality: Surgery doesn't cause breast cancer and it doesn't cause breast cancer to spread, as far as scientists can tell from the research so far. Your doctor may find out during surgery that your cancer is more widespread than previously thought, however. And some animal studies have shown that removing the primary tumor sometimes enables metastatic cancers to grow, but only temporarily; this has not been demonstrated in humans.