Abstract / Summary
Abstract Background Granulomatous lobular mastitis (GLM) is a chronic inflammatory breast entity with unclear etiology and lack of standardized treatment recommendations, causing therapeutic challenges for surgeon. Erythema nodosum (EN) is a rare but recognized extra-mammary manifestation of GLM presented with reddish, tender nodules. In this study, we analyzed the characteristics of GLM patients coexisting with EN. Methods Fifty-two patients with EN out of 480 GLM patients (10.83%) at Shuguang Hospital affiliated to Shanghai University of Traditional Chinese Medicine inpatient mammary department were enrolled from August 2020 to January 2023, and followed up until April 2023. Collected data related to the demographic and clinical characteristics, pathological variants, radiological findings, laboratory tests, management approaches and follow-up outcomes. Results All patients presented with tender mass and breast abscesses, complicated with fistulas and sinuses (55.77%). A majority of EN cases (71.15%) were located symmetrical and bilaterally on the lower limbs, accompanied with arthralgia (61.54%) and arthritis (38.46%). Pathological examinations from 48 cases showed 35.42% of patients were positive on Gram staining, whereas all cases were negative on PAS and ZN acid-fast staining for identifying fungi and tuberculosis. As for contrast-enhanced magnetic resonance imaging (MRI), non-mass-like enhancement (NME) (100%) was commonly with clustered ring-like (90.38%) and heterogeneous (86.54%) enhancement patterns, and multiple regions (44.23%), diffuse (28.85%) and regional (21.15%) distribution. A subset of GLM patients coexisting with EN presented predominantly with increased levels of WBC, NE, CRP, ESR, PRL, C4, IgG, IgE, IgA, CD3 + CD4 + T cell, CD3 + CD8 + T cell, IL-1β, IL-6 and IL-8, and decreased levels of Tregs. Surgery combined with antibiotics and corticosteroids (67.31%), surgery combined with antibiotics (21.15%), and the drug combination of antibiotics and corticosteroids (7.69%) were the preferred treatment strategies. The median follow-up time was 18 (3–33) months, with the recurrence rate of 3.85%, and the rate of de novo lesion in ipsilateral and contralateral breast (7.69% and 7.69%, respectively). Conclusion This study demonstrated GLM patients with EN across multiple perspectives, including clinical manifestations, pathological findings, imaging features, laboratory examinations, therapeutic strategies, and prognosis, providing a comprehensive analysis of the characteristics based on clinical grounds.