Tumefactive multiple sclerosis is a condition in which the central nervous system

Central nervous system

The central nervous system is the part of the nervous system that integrates the information that it receives from, and coordinates the activity of, all parts of the bodies of bilaterian animals—that is, all multicellular animals except sponges and radially symmetric animals such as jellyfish...

 of a person has multiple demyelinating lesions with atypical characteristics for those of standard multiple sclerosis

Multiple sclerosis

Multiple sclerosis is an inflammatory disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged, leading to demyelination and scarring as well as a broad spectrum of signs and symptoms...

, including a size greater than 2 cm, presence of a mass effect

Mass effect (medicine)

In medicine, a mass effect is the effect of a growing mass , for example the consequences of a growing cancer....

, edema

Edema

Edema or oedema ; both words from the Greek , oídēma "swelling"), formerly known as dropsy or hydropsy, is an abnormal accumulation of fluid beneath the skin or in one or more cavities of the body that produces swelling...

, or ring enhancement

Ring-enhancing lesion

A ring-enhancing lesion is an abnormal finding on CT scan obtained using radiocontrast. On the image there is an area of decreased density surrounded by a bright rim from concentration of the enhancing contrast dye. This can be a finding in numerous disease states...

.

These atypical characteristics can mimic other diseases, lead to misdiagnosis, and may require brain biopsy for diagnosis. One Mayo Clinic

Mayo Clinic

Mayo Clinic is a not-for-profit medical practice and medical research group specializing in treating difficult patients . Patients are referred to Mayo Clinic from across the U.S. and the world, and it is known for innovative and effective treatments. Mayo Clinic is known for being at the top of...

 study found that 6% of all lesions with T2 hypointense borders on MRI were in fact tumefactive multiple sclerosis lesions. The more common pathologies included glioma

Glioma

A glioma is a type of tumor that starts in the brain or spine. It is called a glioma because it arises from glial cells. The most common site of gliomas is the brain.-By type of cell:...

s (40%), metastases (30%) and abscess

Abscess

An abscess is a collection of pus that has accumulated in a cavity formed by the tissue in which the pus resides due to an infectious process or other foreign materials...

es (8%).