Malignant Transformation of a Pediatric Intracranial Nongerminomatous Germ Cell Tumor to Embryonal Rhabdomyosarcoma: Case Report and Literature Review.

Malignant transformation of intracranial nongerminomatous germ cell tumors (NGGCTs) is a rare but clinically relevant phenomenon. We present the case of a 13-year-old boy with a localized, pineal NGGCT. After an initial favorable response, tumor growth was noted while still on chemotherapy. Histopathologic characterization revealed that 40% of the tumor was embryonal rhabdomyosarcoma (RMS), consistent with potential malignant transformation. Due to the rare nature of NGGCT malignant transformation, the best clinical approach to these cases remains unclear. We explore existing cases, treatments, and outcomes of malignant transformation in intracranial NGGCTs to help inform future clinical decision-making and the establishment of treatment guidelines.