An undifferentiated sarcoma with BCOR-CCNB3 fusion transcript - pathological and clinical retrospective study.

The BCOR-CCNB3 positive sarcoma is a recently identified sarcoma morphologically and clinically similar to Ewing sarcoma in adolescents and young adults. The BCOR-CCNB3 fusion transcript originates from a paracentric inversion on the X chromosome with an in-frame fusion between the last codon of BCOR and the exon 5 of CCNB3 gene. We report morphological and molecular genetic analysis of 8 undifferentiated sarcomas positive for the BCOR-CCNB3 fusion. Six of the eight BCOR-CCNB3 positive sarcoma patients were male. Five of the eight patients were in their second decade of life (median of all patients 14 years at diagnosis). The bone marrow involvement was demonstrated in 2 of 4 patients tested. Detection of the fusion transcripts BCOR-CCNB3 in the bone marrow suggests that patients with positive findings are at high risk of the tumor progression.