leptomeningeal carcinoma
Meaning of leptomeningeal carcinoma: Cancer that stops behaving like a lump and starts behaving like a fluid, settling wherever spinal fluid happens to flow.
Definition of leptomeningeal carcinoma
Leptomeningeal carcinoma is the spread of cancer cells onto the leptomeninges, the two innermost coverings of the brain and spinal cord, and into the fluid circulating between them. The cells drift in that fluid and settle anywhere along the nervous system, so problems appear at several unconnected sites at once. It arises late in the course of an already advanced cancer.
What are the leptomeninges?
Three membranes wrap the brain and spinal cord. The outer one is tough and leathery. Inside it lies a delicate web-like layer, and beneath that a filmy sheet that clings to every fold of the brain surface. Those inner two are the leptomeninges, and the space between them holds cerebrospinal fluid, which cushions the brain and runs the length of the spinal canal to the base of the spine. Anything shed into that fluid is carried around the entire nervous system within hours, which is exactly what makes this pattern of spread so different from a solid deposit.
How do cancer cells reach it?
By several routes. Cells arrive through the bloodstream and cross into the fluid at the sites where it is produced. They creep inward along the sheaths of nerves and small vessels. A deposit already sitting in the brain or in a vertebra can break through into the adjacent space, and cells are occasionally seeded during surgery on a nearby tumor. Once free in the fluid they no longer need to invade anything to travel, and they settle in a thin coat rather than as a mass, which is why imaging shows lines of enhancement following surfaces and nerve roots rather than a round shadow.
Which cancers cause it?
| Source | Note |
|---|---|
| Breast cancer | The most frequent solid tumor source |
| Lung cancer | Common, and often the first sign of widespread spread |
| Melanoma | The strongest tendency relative to how often it occurs |
| Leukemia and lymphoma | Frequent, and named separately as meningeal disease |
Strictly the word carcinoma covers only cancers arising from lining tissue, so the name fits the breast, lung and gut sources and not the blood cancers or melanoma, which is one reason so many alternative names exist for the same finding, among them carcinomatous meningitis. Symptoms are the giveaway: headache with nausea, double vision, a drooping face, hearing loss, weak legs and bladder trouble appearing together point to damage at several levels of the leptomeningeal lining rather than to one lesion.
Also known as
Used in a sentence
Cerebrospinal fluid cytology confirmed leptomeningeal carcinoma from a known breast primary.
Good to know
The leptomeninges are the inner two coverings only, and because cells shed into cerebrospinal fluid travel the whole nervous system, findings at several unrelated levels at once are characteristic rather than coincidental.
Word origin
Where “leptomeningeal carcinoma” comes from
Lepto- comes from the Greek leptos, thin or fine, and meninx is the Greek for membrane, so the leptomeninges are the delicate membranes.