ABSTRACT
Leptomeningeal metastasis (meningeal carcinomatosis, sarcomatosis, lymphomatosis, gliomatosis; ‘‘neoplastic meningitis’’) denotes seeding of malignant cells from systemic or intracranial neoplasms to pia, arachnoid, and ventricular spaces. This occurs in 5% to 15% of patients with systemic cancer (1,2). Adenocarcinomas predominate (usually of breast, lung or gastrointestinal origin), although melanoma, small cell lung cancer, the acute leukemias, and high-grade Non-Hodgkin lymphomas have the highest disease-specific incidence (up to 50% in Burkitt’s and lymphoblastic lymphoma). Risk factors for neuraxis seeding in lymphoid neoplasms include involvement of testis, orbit, paranasal sinuses, skull base or bone marrow, nodal invasion, and elevated lactate dehydrogenase at presentation (3,4). The diagnosis of leptomeningeal involvement is most commonly made six months to three years after the primary tumor is discovered. The meningeal compartment serves as a sanctuary for cancer cells where systemic chemotherapy does not achieve sustained therapeutic levels. This problem has become more relevant with the availability of more effective treatment protocols for various types of systemic cancer with limited penetration across the blood-brain
barrier (taxane-or trastuzumab-based therapy for breast cancer; imatinib mesylate therapy for chronic myelogenous leukemia; and transretinoic acid therapy for promyelocytic leukemia). Meningeal spread of primary brain tumors is mostly encountered in medulloblastoma, germ cell tumors, as well as tumors of the ependyma and the choroid plexus.
