Bilateral Idiopathic Granulomatous Mastitis: A Case of Noncaseating Granulomas in a Patient With Latent Tuberculosis

Abstract

Idiopathic granulomatous mastitis (IGM) is a rare benign inflammatory disease of the breast of unknown etiology. The typical clinical presentation is a unilateral palpable breast mass with pain and overlying skin erythema. IGM remains a diagnosis of exclusion, and it is necessary to exclude all infectious and noninfectious causes of granulomatous disease. Definitive diagnosis of IGM relies on histological examination, demonstrating granulomatous inflammation without caseous necrosis. Common medical treatment entails the use of corticosteroids and other immunosuppressive agents in patients with IGM. We present a rare case of bilateral IGM in a patient found to have latent tuberculosis (TB), and we discuss the challenges of treating IGM in a tuberculin skin test positive patient. The patient is a 44-year-old female veteran with a history of a positive tuberculin skin test who initially presented with a unilateral painful breast mass. She continued to present with recurrent painful breast masses that progressed to bilateral disease. Mammography and breast MRI were suspicious for malignancy and required biopsy. Histopathology revealed noncaseating granulomas. All stains and cultures were negative for mycobacterium. After 3 years, the disease subsided and she did not present with any further recurrences. She was subsequently treated with isoniazid to reduce the risk of TB reactivation. The diagnosis of IGM is challenging and should be considered in the differential diagnosis of persistent or recurrent breast masses. Patients with IGM found to have latent TB are of particular concern, and tuberculous mastitis must be carefully excluded. IGM is generally a self-limiting disease, and treatment options include observation, symptomatic palliation, steroids, and in complicated recurrent cases or cases involving an abscess, surgery may be considered as a last resort. Treatment of IGM in patients with latent TB should be primarily symptomatic, and steroids should not be used.