EFO_1001012 (leptomeningeal metastasis) is primary or secondary neoplasm in the ARACHNOID or SUBARACHNOID SPACE. It appears as a diffuse fibrotic thickening of the MENINGES associated with variable degrees of inflammation. Also known as: Meningeal Carcinomatosis, Meningeal carcinomatosis, leptomeningeal metastases, malignant meningitis (disorder), metastatic malignant neoplasm in the Leptomeninges, metastatic tumor to the Leptomeninges.