Hamza Tariq - Department of Pathology, Rush University Medical Center, Chicago, USA
Alia Noohu Nazarullah - Department of Pathology and Laboratory Medicine, University of Texas Health San Antonio, Texas, USA

Granulomatous Lobular Mastitis (GLM) is a non-neoplastic, inflammatory disease of the breast that most commonly affects women of childbearing age.۱ The most common clinical manifestation of GLM is a unilateral and painful breast lump that raises concern for a malignant breast neoplasm and causes significant distress to the patient. The distress is further augmented by the chronic and relapsing nature of this disease which often results in the formation of sinuses, fistulae, and fluid collections within the breast as well as ulceration of the overlying skin causing serious breast disfigurement.۲ Despite being a benign condition, GLM is a locally aggressive disease that causes long-term pain and discomfort; hence, many patients require incision and drainage of fluid collections, debridement of inflamed tissue, and even mastectomy to alleviate the symptoms. Even though it is a well-recognized clinical entity, there is no consensus in the field regarding optimal patient management. This obscureness concerning optimal treatment guidelines largely stems from the uncertainty in the etiology of GLM. Various mechanisms, such as autoimmunity, hypersensitivity, lactation, trauma, chemical irritation, and hormonal imbalance have been proposed,۳-۷ but the etiology is unclear which explains why the disease is commonly referred to as “idiopathic” granulomatous mastitis.