A breast lump is a growth or swelling that occurs on or around your breast tissue and can have a number of different causes. Most people worry about cancer when they find a breast lump, but most breast lumps are not cancerous. Nevertheless, it is always important to seek further advice from your doctor so that they can rule out anything concerning. Breast tissue is affected by hormones, and women are more likely to be affected by changes in their breast tissue than men. For this reason, it can be common to have breast changes during your monthly period or when breastfeeding.