Subependymal Giant Cell Astrocytoma Without Clinical Evidence of Tuberous Sclerosis Complex: Diagnostic and Molecular Insights—Case Report

Introduction: A subependymal giant cell astrocytoma (SEGA) is a benign tumor typically associated with tuberous sclerosis complex (TSC), an autosomal dominant syndrome. Case report: The patient, a 15-year-old male, presented with headaches, nausea, and visual obscurations, consistent with increased intracranial pressure. Neuroimaging identified a mass in the anterior left lateral ventricle causing unilateral obstruction at the foramen of Monro. During microsurgery, smears showed a low-grade glial tumor with a biphasic mix of elongated astrocytes and large epithelioid-to-gemistocyte-like cells. Gross total resection was achieved. On permanent sections, a tumor with large polygonal, ganglioid, and gemistocytic-like cells was seen. Nuclear pleomorphism, a feature of SEGA, was present. On immunohistochemistry, the tumor was positive for glial fibrillary acidic protein (GFAP), S100, and CD34, and the cells also displayed nuclear staining for TTF-1. A diagnosis of SEGA in the absence of clinical features of TSC was established; however, definitive classification as sporadic remains limited by the lack of molecular data. Conclusions: This case highlights the importance of evaluating intraventricular masses through the integration of lineage-specific immunohistochemical panels to prevent misclassification of pleomorphic giant cells as high-grade gliomas.