Beneath the Surface: Unveiling Idiopathic Granulomatous Mastitis Within a Masquerading Breast Lump.

Background Idiopathic granulomatous mastitis (IGM) is a rare, benign, chronic inflammatory breast disease of uncertain etiology that often mimics malignancy, thus posing significant diagnostic and therapeutic challenges. Aim To evaluate the clinical profile, diagnostic pathways, and management outcomes of IGM in women in Eastern India through a prospective cohort study. Methods This prospective, observational study was conducted from July 2024 to June 2025 at a tertiary care center in Eastern India. Fifty-four female patients presenting with breast complaints suggestive of IGM were recruited. Patients underwent detailed evaluation, including clinical examination, imaging, core needle biopsy, microbiological studies, and individualized management protocols. Follow-up was conducted at one, three, and six months. Results The mean age was 36.1 ± 7.3 years; all 54 (100%) participants were parous. The most common presenting symptom was a palpable breast lump in 48 (88.9%) patients, followed by pain in 38 (70.4%). Bilateral involvement was observed in seven (13.0%). Radiologically, lesions were non-specific, commonly appearing as heteroechoic/hypoechoic masses or abscesses. Histopathology confirmed non-caseating granulomatous mastitis in all 54 (100%) cases. Microbiological cultures were negative in 49 (90.7%). Treatment was individualized: 25 (46.3%) required surgery, and 29 (53.7%) received medical management (steroids, methotrexate, antibiotics). At six months, 34 (63.0%) achieved partial remission, eight (14.8%) attained complete remission, 12 (22.2%) had a chronic/progressive course, and four (7.4%) experienced recurrence. Conclusions IGM remains a clinical diagnostic challenge in Indian practice. Early histopathological confirmation and targeted medical management, especially steroid-based therapy, are essential to minimize morbidity. Multidisciplinary individualized approaches are critical for optimal outcomes; high recurrence rates after surgery highlight the need for avoidant surgical overtreatment.