Demographic characteristics and clinical analysis of patients with plasma cell mastitis: a single-center, retrospective, cross-sectional study.

Background: Plasma cell mastitis (PCM), a rare form of chronic nonbacterial breast inflammation, is characterized pathologically by ductal dilatation and plasma cell infiltration. Despite its increasing global incidence, large-scale studies on PCM remain limited, and its etiology is poorly understood. This study provides extensive descriptive data on the spectrum of PCM's clinical features. Methods: A retrospective cross-sectional analysis was conducted on 1,260 patients with pathologically confirmed PCM treated at the Breast Department of Chongqing Hospital of Traditional Chinese Medicine. Descriptive statistical methods were employed to analyze their demographic data, clinical characteristics, and laboratory indicators. Results: A total of 1,260 patients with PCM were included. Among the patients, the median age was 31 years, the majority reported history of childbirth (92.8%) and breastfeeding for ≥6 months (67.6%), and 44.9% developed PCM within 3 years postpartum. Identifiable inducement factors were present in 656 (52.1%) of patients and were predominantly psychological factors (20.5%). Breast mass was the most common symptom (92.5%), with a median size of 6.8 cm. Lesions were primarily located in the central area including the areola (78.9%). The positive rate of bacterial culture was low at 17.2%. Conclusions: PCM primarily affects women of childbearing age, especially those aged 30-39 years, and a history of delivery and lactation. Typical presentation includes a large inflammatory mass in the areolar region, but there is a low rate of positive bacterial culture.