Malignant brain tumor in an infant showing histopathological features of yolk sac tumor but genetic and epigenetic features of AT/RT.

SMARCA4 pathogenic variants are rarely detected in pediatric brain tumors other than atypical teratoid rhabdoid tumors (AT/RTs) without INI1 deficiency or in some cases of medulloblastoma. Here, we report an atypical intracranial immature teratoma that recurred as a yolk sac tumor with metastatic spinal and lung lesions. Sequencing of the tumor revealed two SMARCA4 variants, including a splice-site variant and a non-synonymous variant of uncertain significance. Additionally, the methylation signature of the tumor was close to that of AT/RTs. Our case might be a yet-unrecognized subtype of pediatric tumors in which inactivation of SMARCA4 contributes to the pathogenesis.