An Infant-Type Hemispheric Glioma With SOX5::ALK: A Novel Fusion.

Infant-type hemispheric glioma (IHG) is a rare pediatric brain tumor with variable response to chemotherapy and radiotherapy. Molecular insights into IHG can be useful in identifying potentially active targeted therapy. A male fetus was found to have congenital hydrocephalus at the gestational age of 37 weeks. Fetal MRI showed a 2.6 × 2.0-cm tumor located at the frontal horn of the left lateral ventricle, involving the left basal nuclei and thalamus. Tumor biopsy at the age of 2 days revealed an IHG consisting of spindle tumor cells with strong expression of GFAP and ALK. Targeted RNA sequencing detected a novel fusion gene of SOX5::ALK. After initial chemotherapy with cyclophosphamide, carboplatin, and etoposide for 2 cycles, the tumor size progressed markedly and the patient underwent a subtotal resection of brain tumor followed by treatment with lorlatinib, an ALK tyrosine kinase inhibitor with central nervous system (CNS) activity. After 3 months of treatment, reduction of tumor size was observed. After 14 months of treatment, partial response was achieved, and the infant had normal growth and development. In conclusion, we identified a case of congenital IHG with a novel SOX5::ALK fusion that had progressed after chemotherapy and showed partial response and clinical benefit after treatment with the CNS-active ALK inhibitor lorlatinib.