Mastitis Quiz: Ace Your Exams

A 36-year-old woman presents to the clinic with a two-week history of pain and swelling in her right breast with purulent discharge from the right nipple. She has had three similar episodes in the past year; each was less severe, resolved partially with antibiotics, and did not involve nipple discharge. She completed breastfeeding her youngest child two years ago. She has not had recent trauma to the breast, nipple piercings, or systemic symptoms. There is no family history of breast cancer. Temperature is 37.3°C (99.1°F), heart rate is 80/min, blood pressure is 125/78 mm Hg, and respiratory rate is 17/min. On examination, there is erythema and induration in the upper outer quadrant of the right breast with a tender mass. There is no fluctuance. A small, draining sinus tract is noted in the affected area, with purulent discharge. There is no axillary lymphadenopathy. Which of the following is the most likely diagnosis?