Cerebrospinal Fluid Genomic Profiling as an Adjunct in a Case of Intracranial Germinoma: Utility and Limitations

Background and Clinical Significance: Primary central nervous system (CNS) germinomas are rare intracranial germ cell tumors that predominantly affect children and young adults. Histopathological evaluation remains the diagnostic gold standard; however, molecular characterization has increasingly contributed to tumor classification and biological understanding. Recent advances in cerebrospinal fluid tumor-derived nucleic acid (CSF-tNA) analysis provide an opportunity to identify tumor-associated genomic alterations through minimally invasive testing; however, its ability to distinguish CNS germ cell tumor subtypes has not been established and it should be interpreted as a complementary rather than standalone diagnostic tool. Case Presentation: We report a patient with an intracranial mass whose histopathological examination demonstrated features consistent with germinoma. Immunohistochemistry confirmed the diagnosis. Concurrent CSF-tNA analysis using Summit™ 2.0 assay revealed a 12p gain encompassing KRAS, along with copy number gains of chromosome arms 21q and 1q and losses of chromosome arms 11q, 13q, 5q, and 9q. Although these alterations overlap with molecular profiles reported in CNS germ cell tumors, including recurrent 12p gain and RAS/MAPK pathway activation, they cannot distinguish germinoma from other CNS germ cell tumor subtypes and should be interpreted in conjunction with histopathologic, radiographic, and clinical findings. Conclusions: This case illustrates the potential complementary role of CSF genomic profiling alongside conventional histopathology. CSF-based genomic analysis may contribute to supportive molecular information and may have future applications in disease monitoring rather than definitive tumor classification or subtype discrimination.