BACKGROUND: Idiopathic granulomatous mastitis (IGM) is a rare, chronic inflammatory, and benign breast disease. Its unclear etiology may involve autoimmune reactions, secretion-related factors, and microorganisms. AIM: To analyze data from our IGM patient series and compare potential etiological factors. METHODS: We prospectively collected data using follow-up forms for patients diagnosed with IGM at our breast clinic from September 2014 to December 2020 and analyzed it retrospectively. RESULTS: The study cohort included 220 patients, with a median age of 34 years (range: 20-58). A majority, 217 patients (98.6%), reported a history of breastfeeding, with a median duration of 36 months (range: 0-156). The median interval between the last breastfeeding session and disease onset was 25 (25th-75th percentiles: 15-44) months. Additionally, 116 patients (53.5%) reported breastfeeding-related problems. In 41 surgical patients, dense milky-brown debris in the breast ducts was noted. Although no independent seasonal fluctuations in disease onset were detected, a reduction in IGM cases during the summer months was found to correlate with a general decrease in all breast clinic visits. CONCLUSION: Most patients reported recent breastfeeding and half experienced related problems, supporting the secretion theory's relevance in IGM's etiology. The absence of seasonal fluctuations suggests that secretion-related factors may be more central to IGM development than autoimmunity or infections. These findings offer crucial insights for future research into IGM's complex causes.