Supratentorial ependymomas (ST EPNs) are molecularly characterized, of which the RELA fusion positive tumors are the most common and aggressive subgroup. Moreover, histologically, anaplastic ST EPN (ST-AE) often mimic other central nervous system primary high-grade tumors resulting in a diagnostic dilemma. We aimed to study a cohort of ST-AE; evaluate the expression of two RELA fusion-associated markers-L1CAM and p65 (NF-κB); and correlate their expression with clinical and histological parameters. Cases of ST-AE diagnosed in our department from January 2011 to June 2016 (n = 72) were reviewed. A battery of immunohistochemical markers was employed. A total of 65 confirmed ST-AE were included in the study. Age ranged from 9 months to 60 years. There was a slight predominance in the pediatric population (57%). Male-to-female ratio was 1:1.16. Histomorphological features were varied and mimicked other high-grade tumors in several cases. L1CAM immunopositive tumors constituted 26% of cases and were predominantly seen in young children, in the frontoparietal location, and exhibited clear cell morphology with calcification. A consistent pattern of L1CAM immunopositivity was noted in paired primary and recurrent tumor samples. Our study portrays the varied clinical and histomorphological spectrum of ST-AE. The study emphasizes the association of L1CAM immunopositivity with a wide spectrum of histological parameters, literature on which is scant till date. Since ST EPN-RELA are tumors with aggressive behavior, such a correlation would be clinically relevant, particularly when there is limited access to molecular testing.
Keywords: L1CAM; RELA fusion; histomorphological spectrum; p65; supratentorial anaplastic ependymoma.