A 30-year-old lactating woman presents to the clinic with a painful, red, and swollen area on her right breast. The affected area is warm to the touch and tender to palpation. She reports fever, chills, and malaise. On physical examination, a fluctuant mass is palpable in the right breast. A diagnosis of breast abscess is made. However, the patient declines treatment. Which complication can occur if a breast abscess is left untreated?