I would recommend biopsy if you're high risk. Also lobular breast cancer is notoriously difficult to see on imaging and often only shows on breast MRI (not visible on US or mammo). Unfortunately many BC organizations continue to propagate the info that all breast cancers are caught early on mammos and its just not true, especially if you have high breast density. Mammos are not very accurate in premenstrual women compared to postmenopausal women due to the difference in density. Ductal cancer is typically visible on mammos starting as DCIS stage 0 or early invasive stage 1. Since 80% of BCs are ductal, that is often what the focus is, but the remaining 20% are still invasive cancers and need other imaging. The downside to breast MRI is that is does have at least twice the rate of false positives compared to mammos. If you're facility happens to have contrast enhanced mammos (CEM), you could ask if that would help in determining if its malignant or not. Good luck to you that everything is benign.