Primary Intracranial Sarcomas in Peruvian Children: A High-Incidence Clinicopathological Series from a National Reference Center

Background/Objectives: Primary intracranial sarcoma, DICER1 -mutant, is a recently recognized entity in the WHO classification of central nervous system (CNS) tumors and represents an aggressive subgroup of mesenchymal, non-meningothelial neoplasms. Although globally rare, these tumors show an unusually high incidence in Peru, where they constitute the second most common high-grade pediatric CNS malignancy after medulloblastoma. This study aimed to describe their clinicopathological features and outcomes in a large national cohort. Methods: We retrospectively analyzed 112 pediatric cases diagnosed between 2011 and 2025 at the National Cancer Institute of Peru (INEN), integrating histopathology, immunohistochemistry, and clinical outcomes. Results: The median age was 7 years, and most tumors were supratentorial, predominantly affecting the frontal and parietal lobes. Histologically, they exhibited spindle, pleomorphic, and undifferentiated round cell patterns, with frequent hyaline globules and aberrant vasculature. Immunohistochemistry showed recurrent ATRX loss, p53 overexpression, and high proliferative indices, whereas myogenic markers were variably expressed. Median overall survival was 25 months, with 12-, 36-, and 60-month survival rates of 65.7%, 45.9%, and 44.0%, respectively. None of the tested markers (ATRX, p53, Ki-67) demonstrated prognostic significance. Conclusions: This is the largest pediatric series of DICER1 -mutant primary intracranial sarcomas reported from a low- and middle-income country. The findings confirm their poor prognosis and biological heterogeneity, highlighting the urgent need for integrated molecular and epidemiological research to identify risk factors and improve patient outcomes.