A Case of Cystic Neutrophilic Granulomatous Mastitis in a Young Breastfeeding Woman

Cystic neutrophilic granulomatous mastitis (CNGM) is a rare, benign inflammatory breast condition with an unclear etiology. Proposed theories include infection and autoimmune conditions. CNGM often mimics infectious mastitis and inflammatory breast carcinoma, making diagnosis a challenge, especially in breastfeeding patients. Here, we present the case of a 29-year-old breastfeeding woman who developed a painful, ulcerating left breast mass initially suspected to be mastitis or malignancy. Imaging revealed a mixed solid and cystic lesion, and biopsy confirmed CNGM. Her symptoms improved with cephalexin and corticosteroid therapy, and the lesion resolved over two months. This case highlights the diagnostic challenges posed by CNGM and underscores the importance of biopsy for accurate diagnosis. It further suggests that both microbial and immune-mediated processes may contribute to disease development and response to therapy. Continued research is needed to clarify the roles of infectious and autoimmune factors in the pathogenesis and how these etiologies drive the management of CNGM.