Maxillary mesenchymal chondrosarcoma harboring HEY1::NCOA2 fusion in a 13-year-old girl: a rare case report and literature review
Frontiers in Pediatrics, cilt.14, 2026 (SCI-Expanded, Scopus)
- Yayın Türü: Makale / Tam Makale
- Cilt numarası: 14
- Basım Tarihi: 2026
- Doi Numarası: 10.3389/fped.2026.1758538
- Dergi Adı: Frontiers in Pediatrics
- Derginin Tarandığı İndeksler: Science Citation Index Expanded (SCI-EXPANDED), Scopus, EMBASE, Directory of Open Access Journals
- Anahtar Kelimeler: HEY1::NCOA2 fusion, maxillary sinus tumor, mesenchymal chondrosarcoma, pediatric sarcoma, RNA sequencing, sirolimus, targeted therapy
- Açık Arşiv Koleksiyonu: AVESİS Açık Erişim Koleksiyonu
- Sağlık Bilimleri Üniversitesi Adresli: Evet
Özet
Background: Mesenchymal chondrosarcoma (MCS) is a rare and highly aggressive subtype of chondrosarcoma, accounting for less than 1% of all chondrosarcomas. It predominantly affects adolescents and young adults and frequently arises in craniofacial bones and soft tissues. Diagnosis is challenging because of significant histological overlap with other high-grade spindle cell sarcomas, particularly when the cartilaginous component is minimal or absent. The identification of the HEY1::NCOA2 gene fusion has emerged as a highly specific molecular marker for MCS, substantially improving diagnostic accuracy and providing potential therapeutic implications. Case presentation: We report the case of a 13-year-old girl who presented with a 3-month history of progressive right cheek swelling. Imaging revealed a destructive mass in the right maxillary sinus. Histopathological evaluation demonstrated a high-grade spindle cell tumor, initially interpreted as fibrosarcoma, showing diffuse vimentin positivity, a high Ki-67 proliferation index (35%–40%), and CD34 negativity. Comprehensive molecular analysis confirmed a pathogenic HEY1::NCOA2 gene fusion, while ETV6::NTRK3 fusion was excluded. The patient was treated with VAC chemotherapy (vincristine, actinomycin D, cyclophosphamide), local radiotherapy (60 Gy), cranial prophylactic radiotherapy (12 Gy), and subsequent debulking surgery. Follow-up 18F-FDG PET/CT demonstrated a partial metabolic response. Given persistent disease and molecular evidence suggesting activation of the PI3K/AKT/mTOR pathway in MCS, maintenance therapy with the mTOR inhibitor sirolimus was initiated. Conclusion: This case highlights the pivotal role of molecular diagnostics—particularly RNA sequencing—in establishing the diagnosis of mesenchymal chondrosarcoma and differentiating it from other high-grade pediatric sarcomas with overlapping morphology. Identification of the HEY1::NCOA2 fusion not only confirms the diagnosis but may also support biologically targeted therapeutic strategies. Multimodal treatment incorporating chemotherapy, radiotherapy, surgery, and targeted maintenance therapy can achieve meaningful disease control in aggressive craniofacial MCS. To our knowledge, this represents one of the very few reported pediatric cases of maxillary MCS with confirmed HEY1::NCOA2 fusion managed with sirolimus-based maintenance therapy.