PATH-21. An adult primary intracranial sarcoma, <i>DICER-1</i> mutant patient with germline <i>TP53</i> mutation of uncertain significance

Abstract Primary intracranial sarcoma, DICER-1 mutant is a rare highly malignant mesenchymal nonmeningothelial tumor that can be associated with familial DICER1 syndrome and neurofibromatosis type 1. Due to the rarity of these tumors, treatment options for these patients remain poorly defined. Here we present a case of a 21-year-old man of Peruvian background and no significant past medical history who presented with a severe frontal headache associated with nausea and vomiting and loss of consciousness concerning for a seizure. Brain MRI with and without contrast demonstrated an incompletely peripherally-enhancing right frontal lobe mass measuring 3.1 cm with adjacent parenchymal hematoma. The mass was resected and the pathology was consistent with primary intracranial sarcoma, DICER-1 mutant with DICER1 mutation p.D1709G and PDGFRA mutation. He received 2 cycles of ifosfamide, carboplatin, etoposide (ICE) chemotherapy, then proton volumetric modulated arc therapy (14Gy/7Fx) and intensity-modulated radiation therapy (46Gy/23Fx) to the right frontal lobe, followed by 6 additional cycles of ICE chemotherapy. He has been radiographically stable for 8 months post resection. Of note, germline testing demonstrated a TP53 (c.440T&amp;gt;C, p.Val147Ala) variant of uncertain significance. He has a maternal aunt who passed away from stomach cancer at age 31. Given his early development of this tumor and the family history it is possible that this variant may represent an uncharacterized mutation for Li-Fraumeni syndrome.