Clinical Characteristics and Medical Management of Idiopathic Granulomatous Mastitis

Idiopathic (chronic) granulomatous mastitis (IGM) is a rare breast condition that may mimic bacterial abscesses, malignant neoplasms, and several other breast diseases. A thorough evaluation must be performed in suspected cases to exclude other causes, and heightened suspicion is necessary in diagnosing this often underrecognized condition.^1,2 In this descriptive case series, we sought to better characterize the clinical presentation and to identify potentially successful therapies for IGM.

We consecutively enrolled women referred to our dermatology clinic for evaluation of biopsy-proven IGM from May 1, 2015, to April 30, 2019. No exclusion criteria were applied. This study was approved by the institutional review boards of NYU Langone Medical Center and Bellevue Hospital, both in New York, New York. Written informed consent was obtained from all patients before study inclusion.

Patient data were extracted on demographics, disease presentation, treatments, and clinical response. All patients underwent a comprehensive assessment, including a thorough review of systems and medical history, laboratory workup (including a blood test for tuberculosis [QuantiFERON-TB Gold; QIAGEN], prolactin levels, and angiotensin-converting enzyme levels), chest radiograph, mammogram, and breast ultrasonography with core biopsy (except for 1 patient who did not undergo biopsy because of pregnancy). Bacterial, fungal, and mycobacterial tissue cultures were obtained in all but 4 patients.

Diagnosis of IGM relied on exclusion of other causes through laboratory workup as well as characteristic clinical examination and histopathologic findings of cystic neutrophilic granulomatous mastitis. Clinical improvement was assessed through continued in-clinic evaluations by one or two of us (M.K.P. and A.N.F. [the senior authors]), review of medical records, and clinical photography. Treatment response was defined as partial response (improvement in all clinically significant symptoms, including pain, swelling, erythema, and induration) or complete response (complete resolution of the aforementioned symptoms). Treatment response was assessed at the initial visit (14 days after commencing therapy), 2 months into treatment, and approximately every 3 months afterward.

Thirty-two women met the inclusion criteria (Table 1), and the mean (SD) age of these participants was 35.6 (5.5) years. Of these women, 26 (81%) were Hispanic, most of whom were from Mexico (15 [47%]).² All cultures tested (n = 28) were negative for microorganisms (bacteria, fungi, or mycobacteria). Pain was present in all 32 patients and scarring in 22 (70%).

Treatment and outcome information for all patients are shown in Table 2. The mean (SD) follow-up time was 14 (12.3) months. Three patients (9%) were lost to follow-up. Among the 29 remaining patients, 23 (79%) were treated with doxycycline, 100 mg twice daily; treatment failed for 6 (26%) of these patients, who required treatment with methotrexate sodium, usually starting at a test dose of 7.5 mg per week and escalating as needed. Among the 16 patients who responded to doxycycline therapy, 8 (50%) experienced complete response and 8 (50%) partial response. Of the 6 patients treated with methotrexate, 3 (50%) had a complete response and 3 (50%) a partial response. No patient received prednisone monotherapy.

The mean (SD) lengths of treatment were 4.6 (2.7) months for patients receiving doxycycline, 12.5 (8.4) months for those receiving methotrexate, and 4.8 (4.4) months for those receiving prednisone. Among the 12 women treated with prednisone, most required only 1 course and 3 (25%) required multiple courses.

This case series of patients with IGM, uniquely conducted within a dermatology clinic, involved a relatively large sample compared with the 5 other studies on granulomatous mastitis conducted within the United States.^2-5 Consistent with findings in the existing literature, IGM occurred predominantly in Hispanic women of childbearing age, although conclusions regarding the demographic distribution of IGM could not be reached in this single-center study. The present study supports the concern that IGM has major implications for quality of life, with a high prevalence of pain and scarring. We found that treatment with doxycycline, 100 mg twice daily, was successful as a first-line therapy, with complete response in 50% of patients in the present study.⁶ Corticosteroid courses in this study were short compared with those in previous studies, which have noted frequent 6- to 12-month courses.² Methotrexate appeared to be a successful second-line therapy in patients with disease that was refractory to doxycycline (complete response in 50%). Although surgical therapy for IGM has been suggested in the literature, no patient in this study required a surgical procedure, suggesting that adequate medical management may alleviate the need for surgical intervention.

This study highlighted the advantage of dermatologic care for this rare condition. Limitations of this study included its single-institution observational design, lack of a validated outcome measure for IGM, and a relatively small sample size; however, to our knowledge, among the US studies on IGM, this sample was the largest. Furthermore, all patients were evaluated and treated by the same clinicians, who directed a standardized diagnostic workup and treatment algorithm. Further study of IGM is warranted.

Accepted for Publication: November 26, 2019.

Corresponding Author: Alisa N. Femia, MD, The Ronald O. Perelman Department of Dermatology, New York University School of Medicine, 240 E 38th St, 11th Floor, New York, NY 10016 (alisa.femia@nyulangone.org).

Published Online: January 22, 2020. doi:10.1001/jamadermatol.2019.4516

Author Contributions: Drs Pomeranz and Femia are co–senior authors. Ms Steuer and Drs Stern, Cobos, Pomeranz, and Femia had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.

Concept and design: Cobos, Castilla, Pomeranz, Femia.

Acquisition, analysis, or interpretation of data: Steuer, Stern, Cobos, Joseph, Pomeranz, Femia.

Drafting of the manuscript: Steuer.

Critical revision of the manuscript for important intellectual content: All authors.

Statistical analysis: Steuer, Stern.

Administrative, technical, or material support: Steuer, Stern, Cobos, Castilla, Joseph, Pomeranz.

Supervision: Pomeranz, Femia.

Conflict of Interest Disclosures: Dr Pomeranz reported being a paid member of the scientific advisory board of Procter & Gamble and receiving royalties from UpToDate. Dr Femia reported receiving royalties from UpToDate. No other disclosures were reported.