Cystic Neutrophilic Granulomatous Mastitis

Granulomatous lobular mastitis (GLM) is an infrequent inflammatory breast disease, which can simulate malignancy on the basis of clinical and imaging features. It is typically found in parous or lactating women. The differential diagnosis of granulomatous mastitis includes infections caused by bacterial, fungal or mycobacterial agents, and autoimmune disorders like rheumatoid arthritis, sarcoidosis, giant cell vasculitis, and granulomatosis with polyangiitis. Cystic neutrophilic granulomatous mastitis (CNGM) is a sporadic sub-type of GLM that can be linked with infection with Gram-positive bacilli, specifically, Corynebacterium. It is characterised by lipogranulomas that comprise of "cystic" spaces lined by neutrophils which may contain Gram-positive rod-shaped bacteria. The majority of cases of GLM are still "idiopathic" as this pattern of inflammation still remains a mystery. We herein report three cases of CNGM and review the relevant literature. Key Words: Granulomatous mastitis, Corynebacterium, Gram-positive rods, Inflammatory breast disease, Cystic neutrophilic granulomatous mastitis.