Subependymal giant cell astrocytoma in the absence of tuberous sclerosis complex: illustrative case.

backgroundThe authors present a rare case of subependymal giant cell astrocytoma (SEGA) in a patient without tuberous sclerosis complex (TSC) and report characteristics of similar cases in the literature via a systematic review. OBSERVATIONS: A healthy 16-year-old male presented with headache and papilledema and was found to have an intraventricular mass. The mass was resected, and pathological analysis revealed SEGA. The patient developed recurrence with hydrocephalus necessitating open resection followed by CSF diversion. Next-generation sequencing was performed on the tumor, which revealed a homozygous TSC2 mutation. Targeted mosaic variant testing was negative in peripheral blood, indicating an acquired, rather than inherited, mutation. This likely represents a single mutation that underwent gene conversion during early astrocyte division. The authors performed a systematic review of the literature and found 59 additional documented cases of SEGA without TSC. Compared with TSC-associated SEGAs, isolated SEGAs tend to occur in older children, have lower rates of gross-total resection and higher rates of recurrence, and are always solitary lesions. LESSONS: Patients without TSC may develop SEGA due to somatic mutations. Thus, SEGA should remain on the differential diagnosis for intraventricular masses. Resection and histopathological diagnosis are usually indicated, especially for those complicated by hydrocephalus. Prognosis is favorable for isolated SEGA. https://thejns.org/doi/10.3171/CASE2566.