High-grade neuroepithelial tumor with BCOR exon 15 internal tandem duplication

【摘要】：Aims: Central nervous system high-grade neuroepithelial tumor with BCOR alteration(CNS HGNETBOCR) represents a distinct molecular entity. The genetic characteristic is the internal tandem duplication within exon 15 of the BCOR transcriptional co-repressor gene(BCOR-ITD), which has also been reported in clear cell sarcomas of the kidney(CCSK), primitive myxoid mesenchymal tumors of infancy(PMMTI), and undifferentiated round cell sarcomas(URCS).Methods and results: The clinical, pathological, and molecular characteristics of four cases of HGNETBOCR were presented in this study. Three cases occurred in infants(23 months to 4 years old) and one case was 13 years old teenager. The tumors were located in the cerebellum(two cases), frontal lobe(one case) and parietal lobe(one case). On magnetic resonance imaging, a large and wellcircumscribed mass with inconspicuous enhancement was revealed in each case. Histologically, the tumors were composed of spindle to ovoid cells, prone to forming perivascular pseudorosettes and palisading necrosis, but absence of microvascular proliferation. Immunohistochemistry showed that the tumor cells were diffusely positive for BCOR, SOX2, CD133, Nestin, CD56, CD99, Vimentin, and focally positive for Olig-2, S100, SOX10, Syn. GFAP was negative and Ki-67 index was about 20% to40%. BCOR-ITD was found in all 4 cases with the duplicated sequences between87 bp and 119 bp.Conclusion: As a new entity of central nervous system tumors, CNS HGNET-BCOR has unique clinical,pathological and molecular characteristics, which can be detected by BCOR immunohistochemistry and confirmed by BCOR molecular testing. This study discovered that these tumors express stem cell markers, suggesting that it may be derived from tumor stem cells.