TMET-63. Biochemical Characterization of Rhabdoid Meningioma by Proton Magnetic Resonance Spectroscopy

Rhabdoid meningioma is a rare meningeal tumor, considered to be an aggressive meningioma subtype (WHO Grade-III) if the tumor is associated with highly elevated mitotic activity (≥20 mitoses/10 HPFs) and formation of pseudopapillary growth or rhabdoid cells. With 2016 WHO classification of CNS tumors, these tumors have been placed under WHO grade-I (with rhabdoid features) if the above-mentioned grade-III criteria are lacking. Although rhabdoid meningiomas are well characterized immunohistochemically, there are no reports on the 1H MRS based metabolic profiling of these tumors. Here, we report 1H MRS metabolic profiling of a rhabdoid meningioma. The tumor specimen was collected from a rhabdoid meningioma patient undergoing surgery for the resection of the tumor mass. Tumor sample was extracted in 5% perchloric acid, resulting extract was vacuum dried and reconstituted in D2O containing 1.0 mM DSS-d6 (internal standard). Previously, we have identified the following metabolites in grade-I meningioma tumors: lactate, alanine, acetate, glutamate, succinate, glutamine, aspartate, creatine, phosphocreatine, phosphocholine, glycerophosphocholine, myo-inositol, scyllo-inositol, taurine, hypotaurine, glycine, and phosphoethanolamine. The rhabdoid tumor showed a distinct metabolic profile when compared to the grade-I meningioma. This tumor is characterized by relatively higher levels of lactate (9.48 µmol/g, wet tissue) and very low levels of glutamate (0.55 µmol/g, wet tissue) compared to the grade-I meningiomas (lactate = 5.89 µmol/g, and glutamate = 4.06 µmol/g), suggesting that the meningioma tumors with rhabdoid features are glycolytic in nature with dysregulated mitochondrial metabolism. In addition to the above-mentioned metabolites, rhabdoid meningioma also showed low levels of taurine, glycine, phosphocholine and phosphoethanolamine compared to grade-I meningiomas. Relatively low levels of these metabolites further confirm the less aggressive nature of rhabdoid meningioma. In conclusion, rhabdoid meningioma has a distinct metabolic profile which can be detected by 1H MRS. These findings will help in the differential diagnosis of rhabdoid meningiomas and other histologic subtypes of meningiomas.