Congenital infantile fibrosarcoma with ETV6::NTRK3 fusion of the oropharynx: a case report

초록

Background & objectives: Infantile fbrosarcoma is a malignant fbroblastic tumour that occurs predominantly in infancy, characterized by the ETV6::NTRK3 fusion. It typically presents as a highly vascular mass, often resembling vascular tumours, and shows local aggressiveness with rare metastasis. Methods: We present a case of congenital infantile fbrosarcoma with ETV6::NTRK3 fusion of the oropharynx. A premature male, born at 30 weeks and 5 days due to placental abruption, experienced massive bleeding from a protruding oral mass and died 3 hours later. Prenatal ultrasound and MRI revealed a 7x5 cm solid oropharyngeal mass, suspected as an epignathus. Results: Biopsy showed a hypervascular, solid tumour with features resembling a vascular tumour. Microscopic examination revealed a primitive ovoid/round cell or spindle cell tumour with haemangiopericytoma-like vessels and aggregates of undiferentiated small round cells. Immunohistochemical staining was positive for vimentin, CD99, FLI-1, and glypican. Diferential diagnoses included vascular tumours such as Kaposiform hemangioendothelioma and epignathus. However, next generation sequencing confrmed ETV6::NTRK3 fusion, establishing the diagnosis of infantile fbrosarcoma. Conclusion: This case underscores the diagnostic challenge of congenital infantile fbrosarcoma, often misdiagnosed as other entities such as vascular tumours due to hypervascularity or epignathus due to location. Molecular characterization, particularly identifying ETV6::NTRK3 fusion, is essential for accurate diagnosis. The advent of targeted tyrosine kinase inhibitor therapies may change the management of infantile fbrosarcoma, emphasizing the necessity for precise diagnosis in this rare paediatric malignancy.