Next generation sequencing unravels a gliosarcoma mimicking cerebral osteosarcoma

This study presents a case of a woman with recurrent headaches and nausea. Following initial surgery, the pathological diagnosis suggested primary cerebral osteosarcoma. However, despite osteosarcoma-directed chemotherapy, the patient experienced recurrence. A comprehensive diagnostic revision, including next generation sequencing, revealed mutations typical of glioblastoma. These findings highlight the challenges in the differential diagnosis of gliosarcoma, especially when the typical alternating biphasic pattern is not clearly present. The recurrent tumour displayed extensive chondroblastic osteosarcoma-like areas surrounded by glial tissue with vascular proliferation and atypical glial cells leading to a diagnosis of gliosarcoma. Our findings highlight the benefits of using NGS to assist pathologists in accurately diagnosing brain tumours, particularly in challenging cases. This approach is consistent with the progressive updates introduced by the WHO.