What is the Process to Find Out What Type of Tumor You Have?
Pathology analysis begins with taking a tissue sample from a biopsy or surgical resection and sending the sample to a pathology lab for review. Once lab work is finalized, information about the sample is sent to your physician, who shares it with you.
Unfortunately, ependymoma is sometimes misdiagnosed during this process because it is less common than other glioma tumors. If you feel you need a second opinion, be sure to tell your medical staff. Please view the video and read the information below to learn more about the pathology of ependymoma.
What is the classification system for brain tumors?
The most widely used system for classifying primary brain tumors is the World Health Organization (WHO) system. The WHO uses histopathologic (microscopic) features to classify these tumors.
Unlike other cancers, primary brain tumors generally do not spread (metastasize) outside of the central nervous system (CNS). Because of this tendency not to spread, the Tumor-Node-Metastasis (TNM) staging system widely used for most “solid tumor” cancers is not useful for primary brain tumors.
What is classification based on?
The WHO identifies four major subtypes of ependymomas categorized by:
- Degree of variability of tumor cell appearance (pleomorphism)
- Number of tumor cells proliferating (undergoing mitosis)
- Crowding of tumor cells (increased cellularity)
- Amount of tumor infiltration into the surrounding brain (invasion)
These criteria apply to both pediatric and adult ependymomas. While a tumor may show characteristics from one or more tumor grades, physicians treat patients based on the highest-level tumor grade. Visit our treatment section for more details.
What are the types of ependymoma classification?
The WHO classifies ependymomas into three categories:
Grade I or myxo-papillary ependymomas and sub-ependymomas
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Grade II or low-grade ependymomas
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Grade III or anaplastic ependymoma, which is the more malignant designation
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CERN is currently participating in an international effort to refine this grading system. Efforts include reviewing a larger dataset in terms of differences based on grading and identifying other markers of prognosis. Visit our Projects and Collaboration page to learn more.
What are the characteristics of each type?
Grade I tumors are thought to grow slowly and include myxopapillary and sub-ependymomas. Myxopapillary ependymomas appear as the tumor cells arranged in a papillary pattern around vascularized cores. In one large series of patients with ependymoma, 13 percent of ependymomas were found to be Grade I. These tumors occur most commonly in the bottom of the spinal cord, an area often referred to as the cauda equina. Prognosis is good with survival reports spanning more than 10 years after total or partial resection (tumor removal). Sub-ependymomas are also considered to be a Grade I tumor and appear similar to myxopapillary ependymomas under the microscope. However, rather than be attached to parts of the spinal cord, subependymoma typically are attached to a wall of a ventricle (cerebrospinal fluid filled cavity in the brain). These tumors occur more frequently in middle-aged and older men. Sub-ependymomas also have a good prognosis, and a complete removal of the tumorr may be curative.
The classification of Grade II and Grade III ependymoma and their prognoses are currently debated. WHO Grade II tumors are often referred to as “classic ependymomas.” These tumors are most common in young children. In adults, they are the most common type of spinal glioma. When these tumors develop in the brain, they are often in a ventricle. Although most Grade II ependymomas have very recognizable features by microscopic examination, there are variants of ependymomas that can make the diagnosis more challenging. These include cellular ependymomas, papillary ependymomas, clear cell ependymomas and tanycytic ependymomas. Overall, in surveys of adults with ependymomas, 10-year survival rates of 45 percent were reported.
WHO Grade III tumors are also known as anaplastic ependymomas. Incidence data varies based on reports, with only relatively small series of patients included in each of the publications. The definition of the microscopic characteristics that distinquish a Grade II from a Grade III tumor are are currently being refined. Evidence of active cell division (mitoses) and formation of new tumor blood vessels (neovascularization, a component of angiogenesis) are typical findings in the Grade III tumors.