 STUDY OBJECTIVE This phase II, prospective study will evaluate systemic, intravenous high-dose methotrexate HD-MTX in breast cancer patients with leptomeningeal metastasis LMD. The primary objective is to determine if treatment with systemic intravenous HD-MTX will result in an overall survival OS exceeding 12 weeks among patients with triple negative, HER2-positive, and hormone refractory metastatic breast cancer patients with LMD with and without parenchymal brain involvement. 