A 29-year-old woman comes to the physician for follow-up of a right breast lump. The patient first noticed the lump 4 months ago. It was aspirated at that time, and cytology was negative, but the cyst recurred about 1 month later. The cyst was re-aspirated 2 months ago and, again, the cytology was negative. The lump has recurred. Examination reveals a mass at 10 o'clock, approximately 4 cm from the areola. Ultrasound demonstrates a cystic lesion. Which of the following is the most appropriate next step in management?