TMET-38. BIOCHEMICAL CHARACTERIZATION OF PSAMMOMATOUS MENINGIOMA USING MAGNETIC RESONANCE SPECTROSCOPY

Abstract Psammomatous meningioma is a histologic subtype of meningioma and is presented as a highly calcified intracranial or spinal lesion. Although computed tomography (CT) and short/zero echo-time MRI techniques can detect calcification in tumors, a complete biochemical profile of psammomatous meningiomas is not known. Here, we compare the metabolomic profiles of common meningiomas (WHO grade-I and grade-II) and a psammomatous meningioma using ex vivo proton magnetic resonance spectroscopy (1H MRS). The tumor specimens were collected from meningioma patients undergoing surgery for the resection of the tumor mass. Tumor samples were extracted in 5% perchloric acid, centrifuged, supernatants were vacuum dried and reconstituted in D2O containing 1.0 mM sodium 2,2-dimethyl- 2-silapentane-5-sulfonate-d₆ (DSS-d6, internal standard). Previously, we have identified the following metabolites in grade-I and grade-II meningioma tumors: leucine, isoleucine, valine, lactate, alanine, acetate, glutamate, succinate, glutamine, aspartate, creatine, phosphocreatine, phosphocholine, glycerophosphocholine, myo-inositol, scyllo-inositol, taurine, hypotaurine, glycine, phosphoethanolamine, and glucose. In the current study, psammomatous meningioma also showed the presence of all the above metabolites; however, the levels of these metabolites were lower concentrations compared to the grade-I and grade-II meningiomas, except for lactate. In addition to the above-mentioned metabolites, psammomatous meningioma showed the presence of citrate which was not detected in other meningioma subtypes. Citrate is a major component of bone and the presence of citrate (~614 µM/g, tissue) in psammomatous meningioma could be due to the calcification occurring in these tumors. Surgical pathology report of resected tissue specimen showed clusters and small whorls of meningothelial cells with scattered calcifications, consistent with psammomatous meningioma (WHO grade-I; Ki-67 = 3%). In conclusion, detection of citrate by 1H MRS in meningiomas can be helpful in the differential diagnosis of psammomatous meningiomas.