Intra-Tumoral Injections of Natural Killer Cells for Recurrent Malignant Pediatric Brain Tumors

This study is testing whether injecting natural killer (NK) cells — a type of immune cell — directly into a brain tumor cavity can fight recurrent or progressive malignant brain tumors in children after initial treatment has failed. **You may be eligible if...** - Your child has a recurrent or progressive malignant brain tumor confirmed by biopsy (such as high-grade glioma, gliosarcoma, ependymoma, or intracranial sarcoma) - Your child has already completed first-line treatment - Your child is a candidate for surgical removal of the recurrent tumor, which would leave a cavity large enough to hold the device used for NK cell delivery - Your child is in adequate health to undergo surgery **You may NOT be eligible if...** - The tumor cannot be surgically accessed - The post-surgical cavity is too small for the treatment device - Your child has uncontrolled infections or serious organ problems - Your child cannot safely undergo anesthesia Talk to your doctor to see if this trial is right for you.