Mastitis that develops into an infected pocket of fluid, or breast abscess, usually needs be drained.

• A small abscess can be drained with a needle, sometimes using ultrasound to guide the needle. An injection of local anesthetic medication is used first to numb the skin over the infected breast tissue. This procedure can be done in a doctor's office.
• A large abscess must be cut open (lanced) to let the pus drain out. An injection of local anesthetic medication is usually given first to numb the breast tissue. General anesthesia is usually not needed for this treatment unless the abscess is deep. After the infected area has been drained, it may be left open and packed with sterile gauze or closed with a small tube left in so the pus can drain out. This procedure may be done in a doctor's office or outpatient surgery setting.