First step toward the "fingerprinting" of brain tumors based on synchrotron radiation X-ray fluorescence and multiple discriminant analysis.

Synchrotron-radiation-based X-ray fluorescence was applied to the elemental microimaging of neoplastic tissues in cases of various types of brain tumors. The following cases were studied: glioblastoma multiforme, gemistocytic astrocytoma, oligodendroglioma, anaplastic oligodendroglioma, ganglioglioma, fibrillary astrocytoma, and atypical transitional meningioma. Apart from neoplastic tissue, the analysis included areas of tissue apparently without malignant infiltration. The masses per unit area of P, S, Cl, K, Ca, Fe, Cu, Zn, Br, and Rb were used to construct a diagnostic classifier for brain tumors using multiple discriminant analysis. It was found that S, Cl, Cu, Fe, K, Br, and Zn are the most significant elements in the general discrimination of tumor type. The highest similarity in elemental composition was between atypical transitional meningioma and fibrillary astrocytoma. The smallest differentiation was between glioblastoma multiforme and oligodendroglioma. The mean percentage of correct classifications, estimated according to the a posteriori probabilities procedure, was 99.9%, whereas the mean prediction ability of 87.6% was achieved for ten new cases excluded previously from the model construction. The results showed that multiple discriminant analysis based on elemental composition of tissue may be a potentially valuable method assisting differentiation and/or classification of brain tumors.