Leptomeningeal carcinomatosis occurs in approximately 5% of people with cancer and is usually terminal.

They occur more often in patients with melanoma than many other cancers, and historically these patients have an extremely poor prognosis, with survival ranging from 8-10 weeks (Harstad, Hess, & Groves, 2008)

Carcinomatous meningitis (CM) AKA leptomeningeal carcinomatosis (LMC). Found in up to 8% of patients autopsied with systemic cancer. CM may be the presenting finding in up to 48% of patients with cancer (before the diagnosis cancer is known). Most common primaries: breast cancer, lung cancer, then melanoma.