Abstract
Ependymoma is a rare glial neoplasm of CNS with distinct histomolecular heterogenity. The current grading features are controversial, which affect prognosis. To establish unified histomolecular criteria to distinguish grade II/III ependymomas. The authors reviewed the features of 50 ependymomas. Different histological parameters were used to evaluate grading. Additional markers, L1CAM and H3K27me3, were incorporated into the scoring system. The previous grading were modified to new grading criteria. The mean age of the 50 cases was 10+12 years, with 70% of the tumors located in posterior fossa, and 30% in supratentorium. L1CAM was expressed in 10/15 of ST-EPN and 24/35 of PF-EPND showed loss of H3K27me3 expression. All histological features that help differentiate grade II/III ependymomas revealed significant differences and indicating that single histological feature should not be solely used for grading. A significant difference in recurrence between grade II/III ependymomas was noted (P=0.009). These results indicated that a score of >= 10 is considered grade III. There was a significant difference in tumor grading using the previous and new grading methods. All 25 ependymoma cases that were classified as grade II remained as grade II with the new grading system, while 24% of cases previously classified as grade III were reclassified as grade II.The final phase of this study employed novel histomolecular criteria for grading intracranial ependymoma based on a fixed scoring system. This scoring-grading system must be used in further studies to confirm its accuracy.