There are different types of breast lumps. Although any lump formed by body cells may be referred to technically as a tumor. Not all tumors are malignant (cancerous). Most breast lumps – 80% of those biopsied – are benign (non-cancerous). Following are examples of the most common benign breast conditions which produce lumps.
As we have seen, most breast lumps are benign, non-cancerous cysts or tumors. Although they may require surgical removal to prevent their interfering with normal breast function, they will not invade surrounding tissue; they are not life threatening. source