A pediatric central nervous system tumor with BCOR internal tandem duplication confirmed after initially inconclusive targeted molecular testing: a case report.

Authors

Iori Ozono, Sumihito Nobusawa, Vishwa Jeet Amatya, Koichi Ichimura, Junko Hirato, Yohei Inoue, Takako Yoshioka, Kai Yamasaki, Kohei Fukuoka, Masahiro Sekiguchi, Shuhei Karakawa, Maiko Shimomura, Asuka Fujii, Motohiro Kato, Fumiyuki Yamasaki, Yukio Takeshima, Nobutaka Horie

Published in

Brain tumor pathology. Nov 12, 2026. Epub Nov 12, 2026.

Abstract

Central nervous system (CNS) tumors with BCOR internal tandem duplication (ITD) are a distinct pediatric tumor entity characterized by recurrent exon 15 internal tandem duplication of the BCOR gene and a specific DNA methylation profile. We report a rare case of a 13-month-old girl who presented with a hemorrhagic left parietal tumor. Histopathological examination demonstrated embryonal-like features, including high cellularity, frequent mitoses, perivascular pseudorosette formation, and diffuse nuclear BCOR expression. DNA methylation profiling classified the tumor as a CNS tumor with BCOR internal tandem duplication with a high calibrated score. However, targeted RT-PCR and panel-based genomic analysis did not initially confirm BCOR-ITD. As the histopathological, immunohistochemical, and epigenetic findings strongly supported BCOR-ITD, additional genomic analyses were performed within the Japan Children's Cancer Group-whole-genome sequencing study framework. Re-analysis of genomic data suggested BCOR-ITD, and subsequent whole-genome and RNA sequencing confirmed an in-frame 126-bp duplication in BCOR exon 15. The patient underwent gross total resection followed by multimodal therapy and remains progression-free at 18 months. This case emphasizes the importance of integrating histopathological, immunohistochemical, epigenetic, and genomic findings and illustrates how DNA methylation profiling can strongly support the diagnosis, while genomic analysis confirms the defining genetic alteration.

PMID:
43018829
Bibliographic data and abstract were imported from PubMed on 13 Nov 2026.

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