2070 Background: Around 5% of patients with breast cancers (BC) will develop leptomeningeal metastasis (LM). The incidence may increase. Methods: We reported the description and outcome of 112 consecutive BC patients diagnosed with LM in our institution from 2007 to 2011. Correlations between characteristics and overall survival (OS) were analyzed using usual statistical methods (Kaplan Meier, Log-rank, Cox model). Results: BC were invasive ductal carcinoma in 69.7%. Estrogen and progesterone receptors were detected in respectively 61.6 and 44.6%. HER2 expression was observed in 26%. 23% were triple negative. Median time between BC diagnosis and LM diagnosis was 44 months. At LM diagnosis, median age was 54 and median Performance Status (PS) was 2. CSF cytology and cerebrospinal MRI were positive in respectively 72,5% and 87%. 103 (92%) LM patients received IT liposomal cytarabine as 1st line of treatment (ventricular device in 47%). IT therapy could be associated with systemic treatment in 58% of the cases and cerebral radiotherapy for LM in 14% of the cases. Clinical response after 1st line treatment was observed in 57%, CSF response in 30,5%, MRI response in 62,5%. 24 patients received a 2nd line of IT thiotepa, 6 a 3rd line of IT methotrexate. The more significant prognostic factors (p<0,0001) were initial PS, associated systemic treatment and triple negative BC status. Other significant predictors of OS were thiotepa as 2nd line treatment (p=0,0004), intracranial hypertension at LM diagnosis (p=0,019), associated cerebral radiotherapy (p=0,02), progesterone receptor status (p=0,04). Median OS of the 103 treated patients was 3,8 months (4,75 months for 0-2 PS and 1,6 months for 3-4 PS patients). Conclusions: Median OS was consistent those of other recent cohorts of BC LM. Our results confirm the role of a very early diagnosis, before the degradation of the general status. The association with systemic treatment or cerebral radiotherapy is indicated when possible.