Genomic diagnostics leading to the identification of a TFG-ROS1 fusion in a child with possible atypical meningioma.

Meningiomas are rare in children. They are highly complex, harboring unique clinical and pathological characteristics, and many occur in patients with neurofibromatosis type 2. Hereby, we present a case of a two-year-old boy presented with a diagnostically challenging intraventricular tumor. It was incompletely resected 6 times over 14 months but kept progressing and was ultimately deemed unresectable. Histologically, the tumor was initially classified as schwannoma, but extensive international review concluded it was most likely an atypical meningioma, WHO grade II. Comprehensive genomic profiling revealed a TFG-ROS1 fusion, suggesting that ROS1-signaling pathway alterations were driving the tumor growth. In light of this new information, the possibility of a diagnosis of inflammatory myofibroblastic tumor was considered; however the histopathological results were not conclusive. This specific molecular finding allowed the potential use of precision medicine and the patient was enrolled in the AcSé phase 2 trial with crizotinib (NCT02034981), leading to a prolonged partial tumor response which is persisting since 14 months. This case highlights the value of precision cancer medicine in children.