Abstract: Objective  To clarify the clinical and prognostic characteristics of cystic neutrophilic granulomatous mastitis（CNGM）. Methods  We retrospectively reviewed 204 patients of non-puerperal mastitis in Department of Breast, Shuguang Hospital, Shanghai University of Traditional Chinese Medicine who underwent surgery from July 2019 to August 2021. Demographic, clinical, imaging, treatment, and outcome data were compared between CNGM group and non-CNGM group. Results  One hundred and four patients (51%) were diagnosed as CNGM. Compared with the non-CNGM group, patients with CNGM were more likely to be parous women, with a higher rate of breastfeeding history (P=0.024).Moreover, breast trauma, larger lesion scope, fever, raised white blood cell counts, C-reactive protein levels, erythrocyte sedimentation rate and rim enhancement of non-mass lesion and retromammary space edema on magnetic resonance imaging（MRI） were more commonly occurred in the CNGM group than those in the non-CNGM group (all P<0.05). Logistic regression analysis revealed that breast trauma history and lesion scope correlated with the characteristics of CNGM.Patients in the CNGM group were prescribed steroids more frequently (55.8%  vs 37.0%，P=0.007) and had longer postoperative recovery time (39.5%  vs 27.0%，P=0.007) and higher rates of contralateral onset (16.3%  vs 8.0%，P=0.011). Conclusions  CNGM is a distinctive but not rare type of non-puerperal mastitis with more severe local and systemic inflammatory symptoms, independent pathological diagnosis should be done to guide appropriate treatment and follow-up measures. 

Key words: cystic neutrophilic granulomatous mastitis, clinicopathologic features, radiologic features,  treatment and prognosis