A 30-year-old woman presents with redness, pain, and swelling of her right breast for two weeks. There is no history of fever or trauma to the affected breast. She delivered her first child seven months ago and is still breastfeeding. Her primary care provider prescribed a five-day course of oral amoxicillin/clavulanic acid. However, her symptoms remained unchanged. Her antenatal period was unremarkable. Her medical, surgical, and family histories are unremarkable. In particular, there is no family history of breast cancer or other breast disease. There is no history of allergies. A full blood count is normal, with a leukocyte count of 6,500/mm3 (normal: 4,600-11,000). C-reactive protein (CRP) is 3.0 mg/L (normal: <6) and erythrocyte sedimentation rate (ESR) is 14 mm/1hr (normal: 0-20). Her random plasma glucose is 105 mg/dL (normal: <180).