title: Sarcomatous evolution of oligodendroglioma ("oligosarcoma"): confirmatory report of an uncommon pattern of malignant progression in oligodendroglial tumors.
abstract: By analogy to gliosarcoma, the neologism "oligosarcoma" is to describe an uncommon form of biphasic central nervous system tumor composed of contiguous neuroepithelial and mesenchymal elements, each of which individually meet the criteria of oligodendroglioma and sarcoma, respectively. By virtue of its distinctive genotype (codeletion 1p/19q), oligodendroglioma is a particularly inviting paradigm to test the assumption that such mixed tumors are clonally derived from a glial primary. We observed this constellation in a 41-year-old male who underwent two resection procedures for a recurring right frontal tumor at five years' interval. On imaging, both lesions were contrast-enhancing, and measured 7 cm × 7 cm × 6.8 cm and 7 cm × 6.5 cm × 4cm, respectively. Following the first operation, temozolomide monotherapy was administered. Whereas initial histology showed conventional anaplastic oligodendroglioma, the recurrence consisted mostly of a fibrosarcoma-like, fascicular neoplasm that was immunoreactive for vimentin, smooth muscle actin, S100 protein, and focally epithelial membrane antigen. In between, a subset of otherwise indistinguishable spindle cells expressed GFAP, and focally merged with residues of oligodendroglioma. Molecular testing for loss of heterozygosity confirmed codeletion of 1p/19q in both the primary tumor and the sarcomatous recurrence. Similarly, generalized immunoreactivity for the mutant R132H form of isocitrate dehydrogenase in both lesions indicated an identical mutation of the IDH1 gene. By the above standards, biologically consistent "oligosarcomas" are felt to be exceedingly rare, and possibly participate of a nosologically heterogeneous group of combined glial/mesenchymal lesions that may also include iatrogenically induced second malignancies as well as true collision tumors.
authors.affiliation: Section of Neuropathology, Department of Clinical Pathology, Institute of Pathology, University of Bern, Bern, Switzerland. istvanvajtai@yahoo.com
authors.forename: Istvan
authors.initials: I
authors.lastname: Vajtai
authors.forename: Erik
authors.initials: E
authors.lastname: Vassella
authors.forename: Ekkehard
authors.initials: E
authors.lastname: Hewer
authors.forename: Andreas
authors.initials: A
authors.lastname: Kappeler
authors.forename: Michael M
authors.initials: MM
authors.lastname: Reinert
mesh_terms: D000328:Adult; D018906:Antineoplastic Agents, Alkylating / Q000627:therapeutic use; D001932:Brain Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D002872:Chromosome Deletion; D002878:Chromosomes, Human, Pair 1; D002888:Chromosomes, Human, Pair 19; D003131:Combined Modality Therapy; D003606:Dacarbazine / Q000031:analogs & derivatives / Q000627:therapeutic use; D018450:Disease Progression; D018316:Gliosarcoma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D007521:Isocitrate Dehydrogenase / Q000235:genetics; D008297:Male; D009154:Mutation; D009364:Neoplasm Recurrence, Local; D016609:Neoplasms, Second Primary; D009837:Oligodendroglioma / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D000077204:Temozolomide
chemical_list: D018906:Antineoplastic Agents, Alkylating; D003606:Dacarbazine; D007521:Isocitrate Dehydrogenase; C543588:IDH1 protein, human; D000077204:Temozolomide