Ependymoma Pathology

Pathology is the examination of tissues and body fluids in order to make a diagnosis. This involves taking a tissue sample of the tumor when a biopsy or surgery is done to remove the tumor.  The sample is then sent to a pathologist for review. Once the diagnostic lab report is completed, it is sent to your doctor who shares it with you.

Ependymoma is less common than other brain tumors. In addition, it is sometimes difficult to distinguish it from other tumor types. This can make it difficult to diagnose or a delay may occur. Seeking a second opinion is always a good option when dealing with rare diseases. Contact us if you would like a second opinion.

What is the classification system for ependymomas?

The most widely used system to classify primary brain tumors is the World Health Organization (WHO) system. The WHO uses morphological features to classify these tumors into various “Grades”. This involves examining tissue under a microscope. Unlike other cancers, primary brain and spine tumors generally do not spread (metastasize) outside of the central nervous system (CNS). For this reason, 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 assigns a grade to ependymomas based on the following:

  • Appearance of the tumor cells (pleomorphism)
  • How fast the tumor cells are growing (mitotic count)
  • Crowding of tumor cells (cellularity)
  • Growth of tumor blood vessels (vascular proliferation)
  • How much the tumor has spread into the surrounding normal tissue (invasion)

These criteria apply to both pediatric and adult ependymomas. While a tumor may show characteristics from one or more tumor grades, doctors 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 grades:

Grade I – Myxopapillary Ependymomas and Subependymomas

myxopapillary ependymoma

Grade II – Ependymoma (conventional)


Grade III – Anaplastic Ependymoma (which is the more cancerous)

anaplastic ependymoma

The CERN Foundation is currently participating in an international effort to improve this grading system. Efforts include reviewing data to look for differences based on grading and identifying other signs that will help doctors know the expected course of the cancer and recovery (prognosis). Visit our Project II: Tumor Profiling and Pathology page to learn more.

What are the characteristics of each type?

WHO Grade I – Myxopapillary Ependymoma

  • Slow growing
  • Commonly occurs in young adults in the spinal cord, sometimes in the bottom of the spinal cord, an area referred to as “cauda equina”.
  • Tend to have good long-term survival after surgical resection

WHO Grade I – Subependymoma

  • Slow growing noninvasive tumor
  • Are less cellular masses usually attached to the ventricle wall (cerebrospinal fluid filled cavity in the brain).
  • More common in adults and older men
  • Associated with long-term survival
  • Surgery can be potentially curative

WHO Grade II – Ependymoma (conventional)

  • Most common brain tumor in young children
  • Most common type of spinal glioma in adults
  • Often develop in the ventricles when intracranial
  • Several variants exist making diagnosis challenging:
      • Cellular ependymoma
      • Papillary ependymoma
      • Clear cell ependymoma
      • Tanycytic ependymoma
  • Can potentially recur as a higher grade tumor even after treatment

WHO Grade III Anaplastic Ependymoma

  • Show evidence of increased tumor cell growth compared to conventional ependymoma
  • Show evidence of new blood vessel formation to support active growth
  • Exhibit more aggressive behavior than low grade ependymomas
  • Often require additional treatment after surgery and can recur

The classification of grade II and grade III ependymomas and their prognosis are currently debated. Researchers are currently looking at how to better define the features that set apart a grade II from a grade III tumor.