Astroblastoma-like tumor with an EWSR1::BEND2 fusion in the fourth ventricle: a case report and narrative review.

PURPOSE: To report an EWSR1::BEND2 fusion astroblastoma-like tumor arising in the fourth ventricle of a 7-year-old girl and to highlight the diagnostic value of molecular pathology in astroblastoma-like tumors with an atypical immunophenotype.

METHODS

Clinical, histopathological, immunohistochemical, and molecular findings of the present case are presented.

RESULTS

Despite gross total resection followed by radiotherapy, the patient died 7 months after surgery. Histologically, the tumor showed typical astroblastoma-like morphology but an unusual immunophenotype characterized by complete loss of GFAP and Olig2 expression, focal EMA positivity, and diffuse SOX2 positivity. Because of this atypical immunoprofile, diagnosis was challenging and was ultimately established by molecular testing demonstrating an EWSR1::BEND2 fusion.

CONCLUSION

This case highlights the critical role of molecular pathology in diagnosing astroblastoma-like tumors lacking conventional glial markers and suggests that SOX2 expression may represent a novel immunophenotypic finding in this tumor spectrum.