Primary Intracranial Sarcoma, <i>DICER1</i> -Mutant, Diagnosed by DNA Methylation Profiling in an Adult Patient with Germline <i>DICER1</i> Mutation: A Case Report

Primary intracranial sarcoma, <i>DICER1</i>-mutant, is a rare central nervous system tumor that predominantly affects children, only occasionally described in adults. We report on a 30-year-old man with a primary high-grade tumor initially diagnosed and treated as glioblastoma/gliosarcoma. Nineteen years later, re-evaluation by DNA methylation profiling together with next generation sequencing led to reclassification of the tumor as primary intracranial sarcoma, <i>DICER1</i>-mutant. Subsequent genetic testing confirmed a germline <i>DICER1</i> mutation in both the patient and his son. Remarkably, radical resection of the tumor followed by external radiotherapy resulted in an unusually prolonged relapse-free survival, a course that appears unique among reported adult patients with <i>DICER1</i>-sarcoma. This report highlights the critical role of epigenomic profiling in CNS tumors exhibiting atypical clinical behavior, even decades after initial diagnosis, to achieve precise classification and optimize patient management. A brief review of <i>DICER1</i>-mutant sarcoma and DICER1 syndrome is also presented.