Leptomeningeal carcinomatosis: cancer cells that have spread from somewhere else to the lining tissues surrounding the brain. These tissues are known as the leptomeninges, and carcinomatosis is a term that refers to the spread of a tumor. Because these cancer cells have spread from their origin to this new location, they are referred to as metastatic. Leptomeningeal carcinomatosis is not a true brain cancer. The cancer cells in leptomeningeal carcinomatosis can come from a primary tumor at any location in the body, although lung cancer, breast cancer, and melanoma are among the most common types of cancer that cause this condition. Leptomeningeal carcinomatosis is a less common way for metatstatic cancer to involve the brain and occurs in about 5% of people with cancer. Most commonly, cancers that spread to the brain form one or more solid masses inside the brain tissue. In this case, however, the cancer cells spread out through the lining that coats the brain.
Without treatment, leptomeningeal carcinomatosis is rapidly fatal. With chemotherapy, the survival may be prolonged to an average of 3 to 6 months.
Leptomeningeal carcinomatosis is sometimes referred to as meningeal carcinomatosis.