A subependymoma is a type of brain tumor

Brain tumor

A brain tumor is an intracranial solid neoplasm, a tumor within the brain or the central spinal canal.Brain tumors include all tumors inside the cranium or in the central spinal canal...

; specifically, it is a rare form of ependymal tumor

Ependymal tumor

An ependymal tumor is a type of brain tumor that begins in cells lining the spinal cord central canal or the ventricles . Ependymal tumors may also form in the choroid plexus...

.

The prognosis

Prognosis

Prognosis is a medical term to describe the likely outcome of an illness.When applied to large statistical populations, prognostic estimates can be very accurate: for example the statement "45% of patients with severe septic shock will die within 28 days" can be made with some confidence, because...

 for a subependymoma is better than for most ependymal tumors, and is considered a grade I/IV tumor in the World Health Organization

World Health Organization

The World Health Organization is a specialized agency of the United Nations that acts as a coordinating authority on international public health. Established on 7 April 1948, with headquarters in Geneva, Switzerland, the agency inherited the mandate and resources of its predecessor, the Health...

 (WHO) classification.

They are classically found within the fourth ventricle

Fourth ventricle

The fourth ventricle is one of the four connected fluid-filled cavities within the human brain. These cavities, known collectively as the ventricular system, consist of the left and right lateral ventricles, the third ventricle, and the fourth ventricle...

, typically have a well demarcated interface to normal tissue and do not usually extend into the brain parenchyma

Parenchyma

Parenchyma is a term used to describe a bulk of a substance. It is used in different ways in animals and in plants.The term is New Latin, f. Greek παρέγχυμα - parenkhuma, "visceral flesh", f. παρεγχεῖν - parenkhein, "to pour in" f. para-, "beside" + en-, "in" + khein, "to pour"...

, like ependymoma

Ependymoma

Ependymoma is a tumor that arises from the ependyma, a tissue of the central nervous system. Usually, in pediatric cases the location is intracranial, while in adults it is spinal. The common location of intracranial ependymoma is the fourth ventricle...

s often do.

Diagnosis

The diagnosis is based on tissue, e.g. a biopsy

Brain biopsy

Brain biopsy is the removal of a small piece of brain tissue for the diagnosis of abnormalities of the brain. It is used to diagnose Alzheimer's disease, tumors, infection, inflammation, and other brain disorders....

. Histologically

Histology

Histology is the study of the microscopic anatomy of cells and tissues of plants and animals. It is performed by examining cells and tissues commonly by sectioning and staining; followed by examination under a light microscope or electron microscope...

 subependymomas consistent of microcystic spaces and bland appearing cells without appreciable nuclear atypia

Nuclear atypia

Nuclear atypia refers to abnormal appearance of cell nuclei. It is a term used in cytopathology. Specific abnormalities include pleomorphism....

 or mitoses. The nuclei tend to form clusters.