Central nervous system tumors with BCOR internal tandem duplications: a systematic review of clinical, radiological, and pathological features in 69 cases.

Central nervous system tumors with BCL6 corepressor (BCOR) internal tandem duplications (ITDs) constitute a rare, recently characterized pediatric neoplasm with distinct molecular and histopathological features. To date, 69 cases have been documented in the literature, including our institutional case. These neoplasms predominantly occur in young children, with the cerebellum representing the most frequent anatomical location. Radiologically, these tumors present as large, well-circumscribed masses frequently demonstrating necrosis, hemorrhage, and heterogeneous enhancement. Histologically, they are characterized by a monomorphic cellular population featuring ependymoma-like perivascular pseudorosettes, myxoid stroma, and elevated mitotic activity. Immunohistochemically, these tumors exhibit sparse glial fibrillary acidic protein expression while consistently demonstrating positive staining for vimentin and CD56. The defining molecular hallmark is a heterozygous ITD within exon 15 of the BCOR gene, with insertions ranging from 9 to 42 amino acids in length. BCOR immunohistochemistry reveals nuclear positivity in 97.9% of examined cases, although this finding is not pathognomonic for BCOR ITDs. This comprehensive review synthesizes data from all published cases of this novel tumor entity, providing a detailed analysis of clinical presentation, neuroimaging findings, histopathological features with differential diagnostic considerations, therapeutic approaches, and prognostic outcomes.