1379. Idiopathic Granulomatous Mastitis: Experience at a Cancer Referral Center

Abstract

Background Idiopathic granulomatous mastitis (IGM) is challenging as it is a rare disease with unknown etiology, risk factors difficult to establish, and controversies regarding its treatment. Here we describe demographic and clinical characteristics of patients with IGM diagnosed at a cancer referral center, as well as the microbial isolates and treatment. Methods We reviewed the clinical charts of patients with IGM, diagnosed from 2004 to 2019. Males were excluded. Demographic data, past medical history, signs and symptoms, clinical examination findings, radiological and microbiological results, and treatments were retrieved. Frequencies were calculated for qualitative variables and measures of central tendency and dispersion for quantitative variables. Association between categorical variables was explored with a logistic regression to identify risk factors associated with treatment response. Results Two hundred cases of IGM, with a median age of 38 years, were reviewed. Concerning past medical history data, 66 patients (33.8%) were obese; 45 (30.4%) had used hormonal therapy; 6 (3.4%) had an autoimmune disease; 158 (89.8%) had been pregnant and 100 (77.5%) had breastfed. The most common signs were skin induration (65%), a delimited mass (64.5%), and suppuration (52%). On imaging findings, 53.8% was suspicious for malignancy. Culture was performed on 88 patients (44%), 32 had a microorganism isolated, most commonly Staphylococcus spp. (n=16; 51.6%) and Corynebacterium spp. (n=7; 22.6%). The most common treatment was an antibiotic regimen (n=84, 42%). Improvement was noted with the first-line therapy in 92 patients (46%). Fourteen patients (7%) had persistent symptoms and 46 (23%), relapsed. The presence of fever (OR 11.94; CI95% 1.33-106.80; p=0.027) or induration (OR 2.78; CI95% 1.25-6.19; p=0.012) were associated with a poor response. Conclusion We describe one of the largest IGM series in Latin America, on a population similar to those from other resource-limited countries. Fever and induration were associated to a greater risk of failure to initial treatment. The isolation of Corynebacterium spp. has also been described in other series. The variation of initial therapeutic strategies is an opportunity to standardize treatment by the means of prospective studies. Disclosures All Authors: No reported disclosures.