Beyond breast abscess and malignancy: a case of bilateral idiopathic granulomatous mastitis

Idiopathic granulomatous mastitis (IGM) is a rare, benign, chronic inflammatory breast disease. It often mimics breast cancer or abscess, complicating diagnosis. Accurate identification is essential for guiding therapy, particularly in regions with high prevalence of infectious diseases such as tuberculosis.

A 33-year-old female presented with a 1.5-year history of bilateral painful breast masses, erythema, and sinus tract formation. Imaging demonstrated multiple hypoechoic collections and ductal alterations. Initial management targeting presumed breast abscess with antibiotics and surgical drainage provided only transient relief. Core (true-cut) biopsy revealed epithelioid granulomas with multinucleated giant cells and no neoplastic changes. Infectious causes, including tuberculosis, were excluded via negative Mantoux, sputum examination, and Ziehl-Neelsen tests. Sarcoidosis was ruled out by normal serum angiotensin-converting enzyme, absence of systemic features, and lobulocentric granulomas with mixed inflammatory cells, distinguishing IGM from the well-formed "naked" granulomas seen in sarcoidosis.

Despite negative Mantoux and Ziehl-Neelsen (ZN) staining, empirical antitubercular therapy was initiated due to the paucibacillary nature of tuberculous mastitis and the high likelihood of false-negative results in our TB-endemic region. Subsequent biopsy confirmed IGM. The patient responded excellently to tapered oral corticosteroids combined with methotrexate. This case highlights the diagnostic complexity and the importance of histopathological confirmation to distinguish IGM from infections and other granulomatous diseases.

Bilateral IGM is a therapeutic and diagnostic challenge due to its mimicry of malignancy and infection. Histopathology is critical for accurate diagnosis, and immunosuppressive therapy with corticosteroids and methotrexate can provide effective management, particularly in resource-limited health care settings.