I had a very persistent seroma post mastectomy - with hindsight, two flu like episodes were almost certainly caused by infection. A third landed me in hospital and heavy duty antibiotics for a week. My surgeon was not convinced the core problem had been dealt with and, with my approval, operated to give me a ‘good scrub out’! The post op notes refer to a carbuncle - a multi headed boil. I was a year post mastectomy so plenty of time for a colony of nasty bacteria to develop. My surgeon made the right decision - no more infection and no more seroma. Keeping the nasties at bay, when they naturally occur in your body, is not a walk in the park. Follow up with your surgeon is wise. Wishing you a rapid recovery.