High-grade Subependymal Giant Cell Astrocytoma (SEGA).
SEGAs are classically WHO grade 1 intraventricular lesions that occur in patients with tuberous sclerosis complex (TSC, germline mutations in either TSC1 or TSC2). Rare sporadic cases have been reported.1,2 The patient in this case had no other stigmata of TSC and has not undergone germline testing. SEGAs are histologically characterized by large gemistocytic-like cells with admixed small tumor cells and lymphocytes with a sharp brain to tumor interface. Proliferative indices are often low. These tumors tend to occur in young patients and can be the presenting symptom of TSC. Presenting clinical symptoms included obstructive hydrocephalus, hemorrhage into the lesion, or seizure. Gross total resection is generally curative and recurrences are rare.
High grade SEGA or anaplastic transformation of a low-grade SEGA is exceedingly rare, with only a few case reports describing these entities.3,4 This case shows marked pleomorphism and anaplasia, far beyond what is normally seen in SEGA, as well as high proliferation and necrosis. The main differential diagnostic consideration in this case was glioblastoma, which can also occur in patients with TSC.5,6 The determining diagnostic factor in favor of high-grade SEGA was the lack of definitive brain invasion, and the presence of a sharp brain to tumor interface on a subsequent resection specimen received around the time of the molecular results. The prognosis for this very rare lesion is not clear.
Contributed by Daniel Marker, MD, PhD