There are many causes of breast lumps. Some of these causes are harmless, while others can be painful and/or dangerous. Causes of breast lumps include infections, injuries, non-cancerous growths, and cancer.
Often what is thought of as a "mass" or "lump" is actually normal breast tissue, not cancer. This area of the breast can feel thickened, ridge-like, lumpy or asymmetrical compared with the other breast. When a lump has normal imaging results and is not worrisome on physical exam, it is probably benign. Even when biopsied, most lumps are non-cancerous.