Granulomatous mastitis (GM) is a rare, chronic, non-infectious inflammatory condition of the breast. It is characterized by the formation of granulomas—collections of immune cells—within the breast tissue, typically around the lobules. Since the exact cause remains unknown, it is often referred to as idiopathic granulomatous mastitis (IGM) when systemic disease or infection is absent. GM most often affects women of childbearing age, particularly those who have been pregnant or breastfed within the preceding five years.
The clinical presentation of GM includes a firm, painful breast mass, skin inflammation, and sometimes abscess or fistula formation. Because its symptoms closely mimic those of infectious mastitis or inflammatory breast carcinoma, GM is frequently misdiagnosed initially. This confusion often leads to delayed or inappropriate treatment. The chronic nature of the disease, which tends to wax and wane over months or years, makes establishing an effective treatment plan difficult.
Establishing the Diagnosis
An accurate diagnosis must precede treatment, primarily because GM closely resembles breast malignancy. The initial workup involves clinical examination and imaging to characterize the mass and exclude other possibilities. Both mammography and ultrasound are utilized, though the findings from these methods are not specific to GM.
Ultrasound frequently reveals irregular, heterogeneous masses or collections that may suggest an abscess. Mammography often shows an area of increased, asymmetric density. Since neither technique can definitively distinguish GM from breast cancer, they are useful for localization and assessing disease extent, but not for final diagnosis.
To confirm GM and rule out cancer, a core needle biopsy is required. The pathologist examines the tissue sample for the hallmark sign of GM: non-caseating granulomas, which are tight clusters of epithelioid histiocytes and multinucleated giant cells. The tissue is also sent for microbiological culture to exclude infectious causes, such as tuberculosis or fungal infections. The final diagnosis of idiopathic granulomatous mastitis is a diagnosis of exclusion, made after malignancy and specific infections have been ruled out.
Pharmacological Management
Systemic pharmacological therapy aims to suppress the underlying chronic inflammation of GM. Glucocorticoids, such as Prednisone, are the first-line treatment due to their anti-inflammatory and immunosuppressive effects. Steroid therapy starts with a high dose to control the acute flare-up, followed by a slow, gradual tapering regimen lasting six to twenty-four months.
This long tapering schedule prevents rapid recurrence of symptoms, a known risk when steroids are withdrawn quickly. However, prolonged steroid use carries risks of side effects, including weight gain, mood changes, and bone density loss. Therefore, a steroid-sparing agent is often introduced, especially in cases resistant to steroid monotherapy.
Methotrexate is the most common second-line agent, administered weekly in doses ranging from 15 to 25 milligrams. When combined with steroids, Methotrexate allows for a faster reduction in the steroid dose, minimizing long-term side effects. Azathioprine is another option for patients who cannot tolerate or do not respond to Methotrexate, working by modulating the immune response. Combining a corticosteroid with an immunosuppressive agent is frequently employed to maintain remission and reduce the duration of high-dose steroid exposure.
Surgical Interventions and Refractory Cases
Surgery is generally reserved for GM cases refractory to medical therapy or those complicated by physical manifestations requiring drainage or removal. Indications for surgery include large, painful abscesses unresponsive to aspiration, chronic fistulas (abnormal tracts connecting inflamed tissue to the skin), or localized disease persisting despite medical treatment. Surgery is considered after systemic therapy failure or when medication side effects become intolerable.
For isolated abscesses, Incision and Drainage (I&D) is performed to relieve pressure and remove material, often followed by antibiotics. For persistent, localized disease, a Wide Local Excision (WLE) removes all visible inflammatory tissue. The goal of WLE is to achieve clear margins, but this is challenging due to the diffuse nature of the inflammation.
Surgical treatment must be carefully weighed against the benefits. Wide excisions, especially for large lesions, can result in wound healing problems, delayed healing, and the formation of new fistulas. Furthermore, removing breast tissue can lead to cosmetic deformity and scarring. Recurrence rates following surgery alone can be up to 50%, emphasizing the need to combine excision with medical therapy for lasting remission.
Monitoring and Managing Recurrence
GM has a high rate of recurrence, even after successful initial treatment. This necessitates long-term surveillance to quickly identify and manage flare-ups. Patients require regular physical examinations focused on identifying new lumps, redness, or signs of skin change.
Imaging follow-up, typically using ultrasound, is incorporated into the monitoring schedule to visualize the treated area and detect subclinical inflammation or new mass formation. Recurrence rates can reach 40% after steroid-only therapy and are often higher after surgical intervention alone. The chronic, relapsing nature of the disease must be clearly communicated to the patient to manage expectations and ensure compliance with the surveillance plan.
A flare-up is defined as a return of symptoms or growth of the lesion. Treatment frequently involves re-initiating systemic medical therapy, often restarting glucocorticoids, sometimes combined with an immunosuppressive agent like Methotrexate. Patient education is a foundational component of long-term management, empowering the individual to recognize the earliest signs of relapse, such as localized pain or induration, so that treatment can be restarted promptly.