In some cases, benign (non-cancerous) lumps and nodules may be diagnosed from visual characteristics. Ultrasound is an excellent diagnostic tool that may prevent an unnecessary biopsy. But in other cases, you may need a biopsy to determine if the lesion is cancerous. Biopsies can also determine the type of breast cancer that’s present and how aggressive it may be. Depending on the results of the biopsy, you may also be advised to have biopsies of lymph nodes to determine if the cancer may have spread.