Intraparenchymal mesenchymal chondrosarcoma of the frontal lobe – a case report and molecular detection of specific gene fusions from archival FFPE sample

Abstract

Mesenchymal chondrosarcoma is a rare tumor of cartilaginous origin characterized by its bimorphic pattern composed of highly undifferentiated small round cells separated by islands of well-differentiated hyaline cartilage. It exhibits higher malignancy and earlier occurrence in comparison to classic chondrosarcomas. Recently identified HEY1-NCOA2 and IRF2BP2-CDX1 gene fusions confirm their distinct molecular origin and pose a promising diagnostic marker. The majority of cases arise from craniofacial bones. In this study, we present a rare case of mesenchymal chondrosarcoma encompassed within the brain parenchyma of the frontal lobe without any dural or bone attachment. We demonstrate histopathological findings and confirm the HEY1-NCOA2 gene fusion in a formalin-fixed paraffin-embedded archival sample using simple reverse transcription polymerase chain reaction (RT-PCR) method. IRF2BP2-CDX1 gene fusion was absent in the analyzed sample. The clinical follow-up is also presented with a review of treatment modalities for this entity.