Impact of Targeted Antibiotic Therapy and Infectious Diseases Specialist Input in the Management of Cystic Neutrophilic Granulomatous Mastitis

Objectives: Cystic neutrophilic granulomatous mastitis (CNGM) is a rare cause of destructive inflammatory breast disease which has been linked to the presence of lipophilic Corynebacteria which often show broad resistance to antibiotics. Antibiotic therapy is frequently utilised as an adjunct to surgical management however there is a lack of reported data on optimal antimicrobial strategies and recovery is often prolonged. Methods: We developed a management strategy in a tertiary infectious diseases unit to identify potential Corynebacteria-related CNGM pathology and took a targeted antibiotic-led approach to treatment. Clinical, laboratory, imaging, and therapeutic data were collected retrospectively from patients seen in our clinic between 2016-2020. Results: Thirteen patients were identified who met criteria for the diagnosis of CNGM. The mean age was 42.6 years and all patients were female. All had bacteriological evidence of Corynebacteria infection or granulomatous findings on histology. Microbiological evidence of Corynebacteria was present in 76.9%. Antibiotics were used as first line therapy in 92.6%, with a variety of agents used. Steroids were used as an adjunctive therapy in 53.8%. Most patients underwent surgical drainage or clinic-based aspiration of an abscess as part of their treatment. Eleven of thirteen patients (84.6%) experienced complete resolution of symptoms however recovery was protracted with a median time to resolution of >6 months. Conclusions: We present a case series of a rare clinical entity, CNGM, and highlight the outcomes of implementation of an antibiotic and infection service-led clinical approach in these patients.