Breast lump is a swelling, growth, or mass in the breast tissue. While finding a lump in your breast can be concerning, it’s important to remember that the majority of breast lumps are not breast cancer. There are many conditions that may cause benign (non-cancerous) breast lumps. However, all breast lumps should be investigated by a healthcare professional.Lumps in the breasts can have lots of different causes. They’re often caused by something harmless like a non-cancerous tissue growth (fibroadenoma) or a build-up of fluid (breast cyst).