by Jason Wasserman MD PhD FRCPC
August 7, 2024
This article was written for patients by pathologists. It aims to help patients understand their pathology report for supratentorial ependymoma, YAP1 fusion-positive. It includes sections on its symptoms, causes, genetic changes, diagnosis, WHO grade, and microscopic features.
Supratentorial ependymoma, YAP1 fusion-positive, is a type of brain tumour that arises from ependymal cells, which line the ventricles of the brain and the central canal of the spinal cord. This specific type occurs in the supratentorial region, meaning it is located above the tentorium, a membrane that separates the cerebrum from the cerebellum. These tumours primarily arise in young children. The term “YAP1 fusion-positive” refers to a genetic alteration involving the YAP1 gene that is found in these tumors.
The symptoms of supratentorial ependymoma, YAP1 fusion-positive, can vary depending on the tumour’s location and size but may include:
The exact cause of supratentorial ependymoma, YAP1 fusion-positive, is not fully understood. It is believed to arise from genetic mutations that occur randomly. The presence of the YAP1 gene fusion is a significant factor in the development of these tumors, leading to uncontrolled growth of ependymal cells.
Supratentorial ependymomas with YAP1 fusion are characterized by a specific genetic alteration involving the YAP1 gene. This fusion results in abnormal activity that promotes tumour growth. Identifying this genetic change is crucial for diagnosing and understanding the behavior of the tumour.
The diagnosis of supratentorial ependymoma, YAP1 fusion-positive, is made through a combination of imaging studies and biopsy. Imaging studies such as MRI (Magnetic Resonance Imaging) can reveal the presence and location of the tumour in the brain. A biopsy, which involves taking a small sample of the tumour tissue, is then performed to confirm the diagnosis. The biopsy sample is examined under a microscope by a pathologist, who looks for specific characteristics and performs genetic testing to identify the YAP1 fusion.
When a pathologist examines a biopsy from a supratentorial ependymoma, YAP1 fusion-positive, they look for specific features under the microscope, including:
The World Health Organization (WHO) grade system is used to classify the aggressiveness of brain tumours. Tumors are graded on a scale from 1 to 4, with grade 1 being the least aggressive and grade 4 being the most aggressive.
Supratentorial ependymoma, YAP1 fusion-positive, can be classified as either WHO grade 2 or WHO grade 3:
Various molecular tests can be performed to identify a YAP fusion and confirm the diagnosis. The two most commonly performed tests are next-generation sequencing (NGS) and fluorescence in situ hybridization (FISH).
Next-generation sequencing (NGS):
Fluorescence in situ hybridization (FISH):
Yes, supratentorial ependymoma, YAP1 fusion-positive, can recur after surgery. The likelihood of recurrence depends on several factors, including the completeness of the tumor removal during surgery and the tumor’s WHO grade. Tumors that are completely resected and classified as WHO grade 2 have a lower risk of recurrence compared to those that are partially removed or classified as WHO grade 3. Regular follow-up with imaging studies, such as MRI, is essential to monitor for any signs of recurrence. If the tumor does recur, additional treatments, such as repeat surgery, radiation therapy, or chemotherapy, may be needed to manage the condition.