This alleged obstruction is supposed to cause toxins to accumulate in the breast that eventually lead to breast cancer. But even Breast Cancer Action, which closely monitors possible links between the disease and environmental causes, has debunked the antiperspirant myth. So has the American Cancer Society. Like antiperspirants, underwire bras are reputed in some circles to obstruct lymph flow. Interesting theory, but there's no evidence.
Tenderness associated with a lump, particularly if it's cyclical in nature, is often a good sign.
But many breast tumors that are malignant can be tender as well. It's best to have your doctor check out anything suspicious. At the moment, mammograms are the single most important tool in finding breast tumors. They catch 85 percent of breast tumors, but that still leaves 15 percent that escape detection. For women with dense breasts, breast ultrasound or MRI may be useful along with mammography.