metastatic malignant neoplasm neoplastic meningitis meningeal carcinomatosis leptomeningeal carcinomatosis metastatic malignant neoplasm in the leptomeninges meningeal metastasis carcinomatous meningitis Metastatic neoplasm in which the tumor cells spread to leptomeninges (pia and arachnoid) and subarachnoid space. The most common primary tumors metastasizing to the leptomeninges are breast and lung carcinomas, melanoma, aggressive non-Hodgkin lymphoma, and acute lymphocytic leukemia. MEDGEN:352817 MONDO:0700219 NCIT:C27383 leptomeningeal carcinoma https://github.com/monarch-initiative/mondo/issues/5495 NCIT:C3814 UMLS:C1704231 leptomeningeal metastasis icd11.foundation:262966673