A 35-year-old woman presents with a large, firm, minimally tender subareolar mass in her right breast. She states it has been present for the last month and has continued to grow. While the patient denies a family history of breast cancer, she does have a new 6-month-old child. She denies fevers or chills, and the skin surrounding the mass is devoid of any inflammatory changes. Ultrasound reveals a well-circumscribed hypoechoic cyst-like structure. A fine needle aspiration (FNA) reveals a milky discharge. What is the most appropriate next step in the management of this patient?