DOI: 10.26650/iuitfd.1913731 ISSN: 1305-6441

NF1-ASSOCIATED MIDLINE HIGH-GRADE ASTROCYTOMA WITH PILOID FEATURES ARISING IN THE DORSAL THALAMUS: A DIAGNOSTIC CONSIDERATION

Tuçe Söylemez Akkurt, Ahmet Erbağcı, Ahmet Faruk Özdemir, Fatih Çalış, Baran Canku Karataş, Başak Atalay
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High-grade astrocytoma with piloid features (HGAP) is a recently defined brain tumor entity primarily diagnosed via DNA methylation profiling due to its histological overlap with glioblastoma and pilocytic astrocytoma. We report a 26-year-old man with neurofibromatosis type 1 (NF1) presenting with a high-grade midline lesion involving the thalamus and mesencephalon. Histopathological examination demonstrated a high-grade glial neoplasm with loss of ATRX expression by immunohistochemistry. While HGAP typically occurs in the posterior fossa, NF1-associated cases show a marked predilection for midline locations, complicating the differential diagnosis with other high-grade gliomas. In this case, DNA methylation profiling confirmed the diagnosis with high confidence. Prognostically, HGAP demonstrates an intermediate survival profile, with a 5-year overall survival rate of approximately 50%, which is superior to IDH-wild-type glioblastoma but inferior to conventional pilocytic astrocytoma. Although standardized treatment guidelines are lacking, identifying targetable molecular alterations remains essential for management.

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