Subependymal giant-cell astrocytomas in the absence of tuberous sclerosis

OBJECTIVE Tuberous sclerosis is a rare genetic condition caused by TSC1 or TSC2 mutations that can be inherited, sporadic, or the result of somatic mosaicism. Subependymal giant-cell astrocytoma (SEGA) is a major diagnostic feature of tuberous sclerosis complex (TSC). This study aimed to present a series of cases in which a pathological diagnosis of SEGA was not diagnostic of tuberous sclerosis. METHODS The authors retrospectively reviewed a clinical case series of 5 children who presented with a SEGA tumor to Johns Hopkins All Children's Hospital and St. Louis Children's Hospital between 2010 and 2022 and whose initial genetic workup was negative for tuberous sclerosis. All patients were treated with craniotomy for SEGA resection. TSC genetic testing was performed on all SEGA specimens. RESULTS The children underwent open frontal craniotomy for SEGA resection from the ages of 10 months to 14 years. All cases demonstrated the classic imaging features of SEGA. Four were centered at the foramen of Monro and 1 in the occipital horn. One patient presented with hydrocephalus, 1 with headaches, 1 with hand weakness, 1 with seizures, and 1 with tumor hemorrhage. Somatic TSC1 mutation was present in the SEGA tumors of 2 patients and TSC2 mutation in 1 patient. Germline TSC mutation testing was negative for all 5 cases. No patient had other systemic findings of tuberous sclerosis on ophthalmological, dermatological, neurological, renal, or cardiopulmonary assessments and thus did not meet the clinical criteria for tuberous sclerosis. The average follow-up was 6.7 years. Recurrence was noted in 2 cases, in which 1 patient underwent radiosurgery and 1 was started on a mammalian target of rapamycin (mTOR) inhibitor (rapamycin). CONCLUSIONS There may be intracranial implications of somatic mosaicism associated with tuberous sclerosis. Children who are diagnosed with SEGA do not necessarily have a diagnosis of tuberous sclerosis. Tumors may carry a TSC1 or TSC2 mutation, but germline testing can be negative. These children should continue to be followed with serial cranial imaging for tumor progression, but they may not require the same long-term monitoring as patients who are diagnosed with germline TSC1 or TSC2 mutations.