title: Oncocytic ependymoma: a new morphological variant of high-grade ependymal neoplasm composed of mitochondrion-rich epithelioid cells.
abstract: Oncocytomas are defined as tumors containing in excess of 50% large mitochondrion-rich cells, irrespective of histogenesis and dignity. Along the central neuraxis, oncocytomas are distinctly uncommon but relevant to the differential diagnosis of neoplasia marked by prominent cytoplasmic granularity. We describe an anaplastic ependymoma (WHO grade III) with a prevailing oncocytic component that was surgically resected from the right fronto-insular region of a 43-year-old female. Preoperative imaging showed a fairly circumscribed, partly cystic, contrast-enhancing mass of 2 cm × 2 cm × 1.7 cm. Histology revealed a biphasic neoplasm wherein conventional ependymal features coexisted with plump epithelioid cells replete with brightly eosinophilic granules. Whereas both components displayed an overtly ependymal immunophenotype, including positivity for S100 protein and GFAP, as well as "dot-like" staining for EMA, the oncocytic population also tended to intensely react with the antimitochondrial antibody 113-1. Conversely, failure to bind CD68 indicated absence of significant lysosomal storage. Negative reactions for both pan-cytokeratin (MNF 116) and low molecular weight cytokeratin (CAM 5.2), as well as synaptophysin and thyroglobulin, further assisted in ruling out metastatic carcinoma. In addition to confirming the presence of "zipper-like" intercellular junctions and microvillus-bearing cytoplasmic microlumina, electron microscopy allowed for the pervasive accumulation of mitochondria in tumor cells to be directly visualized. A previously not documented variant, oncocytic ependymoma, is felt to add a reasonably relevant novel item to the differential diagnosis of granule-bearing central nervous system neoplasia, in particular oncocytic meningioma, granular cell astrocytoma, as well as metastatic deposits by oncocytic malignancies from extracranial sites.
authors.affiliation: Section of Neuropathology, Institute of Pathology, University of Bern, Switzerland. istvanvajtai@yahoo.com
authors.forename: Istvan
authors.initials: I
authors.lastname: Vajtai
authors.forename: Michael
authors.initials: M
authors.lastname: von Gunten
authors.forename: Christian
authors.initials: C
authors.lastname: Fung
authors.forename: Caspar
authors.initials: C
authors.lastname: Brekenfeld
authors.forename: Andreas
authors.initials: A
authors.lastname: Kappeler
authors.forename: Michael M
authors.initials: MM
authors.lastname: Reinert
mesh_terms: D018249:Adenoma, Oxyphilic / Q000276:immunology / Q000473:pathology* / Q000648:ultrastructure; D000328:Adult; D001932:Brain Neoplasms / Q000276:immunology / Q000473:pathology* / Q000648:ultrastructure; D003937:Diagnosis, Differential; D004806:Ependymoma / Q000276:immunology / Q000473:pathology* / Q000648:ultrastructure; D015622:Epithelioid Cells / Q000473:pathology / Q000648:ultrastructure*; D005260:Female; D005904:Glial Fibrillary Acidic Protein / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D016130:Immunophenotyping; D007365:Intercellular Junctions / Q000648:ultrastructure; D008279:Magnetic Resonance Imaging; D046529:Microscopy, Electron, Transmission; D008928:Mitochondria / Q000473:pathology / Q000648:ultrastructure*; D009364:Neoplasm Recurrence, Local / Q000473:pathology / Q000532:radiotherapy; D009418:S100 Proteins / Q000276:immunology / Q000378:metabolism
chemical_list: D005904:Glial Fibrillary Acidic Protein; D009418:S100 Proteins