Described is a patient with concurrent discrete gliomas: a pleomorphic xanthoastrocytoma with anaplastic features and ananaplastic oligoastrocytoma. The distinct and morphologically dissimilar tumors demonstrated similar genetic abnormalities by loss ofheterozygosity and comparative genome hybridization. Clonality and proteomic analyses highlighted an independent origin for thetwo tumors. Proteomic methods may prove useful in cases where the differential diagnosis and pathogenetic origin of tumors areuncertain, as well as more globally for its ability to provide insight into specific expression of proteins that may serve as uniquemarkers of tumorigenesis or as novel targets of therapy. Described is a patient with concurrent discrete gliomas: a pleomorphic xanthoastrocytoma with anaplastic features and ananaplastic oligoastrocytoma. The distinct and closely matched genes are similar genetic abnormalities by loss of heterozygosity and comparative genome hybridization. Clonality and proteomic analyzes highlighted an independent origin for thetwo tumors. Proteomic methods may prove useful in cases where the differential diagnosis and pathogenetic origin of tumors areuncertain, as well as more globally for its ability to provide insight into specific expression of proteins that may serve as uniquemarkers of tumorigenesis or as novel targets of therapy.