Idiopathic granulomatous mastitis (IGM) is a rare, benign chronic inflammatory breast condition that can clinically and radiologically mimic breast cancer^[1].  It was first described by Kessler and Wolloch in 1972 ^[2]. The exact cause remains unknown, though an autoimmune response has been proposed. IGM primarily occurs in premenopausal women, often following pregnancy or breastfeeding. Various factors have been proposed to contribute to the etiology of the disease, including hormonal imbalances, autoimmunity, unidentified microbiological agents, smoking, and α1-antitrypsin deficiency^[3]. Interestingly, the prevalence of IGM varies across regions and ethnicities, with higher rates observed in Middle Eastern, Mediterranean, Asian, and Hispanic populations compared to Western Caucasian populations^[3]. Although IGM is a benign condition, it can lead to significant symptoms, including breast pain, abscesses, fistulas, erythema, cosmetic deformities, and psychological distress ^[4]. Treatment remains challenging and may include: antibiotics, corticosteroids, surgical excision and methotrexate^[5].

Radiology is integral to managing IGM, supporting diagnosis, follow-up, and treatment. Diagnostic imaging modalities, including ultrasound and MRI, alongside biopsy, are vital for confirming the condition For follow-up, ultrasound and MRI play a key role in monitoring disease progression and evaluating treatment response. Furthermore, radiology contributes to treatment, notably through procedures such as ultrasound-guided intralesional steroid injections.^[6].

IGM can share certain imaging and clinical features with breast cancer, particularly inflammatory breast cancer (IBC), making differentiation between the two challenging. Given that these diseases require entirely different management and treatment approaches, accurate and timely diagnosis is crucial. This educational poster highlights the multimodality imaging characteristics of IGM, discusses its overlapping features with IBC, and, most importantly, identifies key imaging differences to aid in differentiation. The poster will present imaging findings from IGM cases alongside relevant clinical information to provide a comprehensive understanding.