Beyond Inflammation: Decoding the Bacterial Landscape of Granulomatous Mastitis

Background: Idiopathic granulomatous mastitis (IGM) is a rare, chronic inflammatory breast disease with an unclear etiology. This study aimed to investigate the potential microbial involvement in IGM by detecting bacterial DNA in biopsy samples. Methods: This cross-sectional study included 22 patients with histopathologically confirmed IGM, selected through convenience sampling from Besat Hospital, Sanandaj, Iran, in 2019. DNA was extracted from biopsy samples, and the 16S rRNA gene was amplified using universal primers. The amplified products were sequenced, and bacterial species were identified using NCBI BLAST. Results: The mean age of the patients was 35.23 years. DNA analysis revealed Escherichia coli in 21 of 22 samples (95.5%) and Staphylococcus lugdunensis in 1 sample (4.5%). The most common inflammatory symptom was erythema, observed in 8 patients (36.4%), while deep collections were the most frequent tissue abnormality, found in 10 patients (45.5%). Conclusion: The detection of E. coli in most samples suggests a potential bacterial role in IGM pathogenesis. Further research, including control samples from normal breast tissue, is needed to validate these findings and evaluate the potential benefits of molecular testing in clinical practice.