L1CAM Immunopositivity in Anaplastic Supratentorial Ependymomas: Correlation With Clinical and Histological Parameters.

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.