Hi Lisa ! Good evening. I am Dr Shareef answering your query. Considering that you aunty has been confirmed BRCA1 positive, the lump in your breast needs close observation, with a present physical examination by a general surgeon followed by an ultrasound of bilateral breast and axilla followed by a mammogram bilateral breast. Your treating surgeon might advise you for an excision biopsy for ruling out chances of any malignancy, although it does not look like from the history of changing size with menstrual cycle, which usually occurs with simple fibroadenosis. The management would at the end depend on the clinical findings in breast with axilla, along with results of related investigations. I hope this information would help you in discussing with your family physician/treating doctor in further management of your problem. Please do not hesitate to ask in case of any further doubts. Thanks for choosing health care magic to clear doubts on your health problems. Wishing you an early recovery. Dr Shareef.