title: Epithelioid versus rhabdoid glioblastomas are distinguished by monosomy 22 and immunohistochemical expression of INI-1 but not claudin 6.
abstract: Epithelioid and rhabdoid glioblastomas are rare entities that share some overlapping morphologic features, but remain poorly characterized at the immunohistochemical and genetic level. We report 10 examples: 8 epithelioid glioblastomas (E-GBMs) and 2 rhabdoid GBMs (R-GBMs). E-GBMs tended to be superficially located, circumscribed, supratentorial tumors composed of monotonous, discohesive sheets of small rounded cells that mimicked metastatic malignant melanoma. R-GBMs showed tumor with classic rhabdoid features arising as a subpopulation of an otherwise classic GBM, fitting the definition of composite extrarenal rhabdoid tumors. Polyphenotypic immunohistochemical expression and focal loss of INI-1 protein in the rhabdoid areas of R-GBMs distinguished them from E-GBMs. Monosomy 22 was identified in R-GBMs, but not E-GBMs. Immunostaining for claudin-6, a key component of tight junctions that we have earlier shown to be a positive cytoplasmic immunohistochemical marker for atypical teratoid or rhabdoid tumors (AT/RTs), was also conducted. None of the E-GBMs or R-GBMs showed claudin-6 cytoplasmic expression, including the focal areas in the 2 R-GBMs in which there was loss of INI-1 protein nuclear expression. Thus, in the CNS, claudin-6 expression may be a good discriminator of atypical teratoid or rhabdoid tumors from other CNS rhabdoid or epithelioid neoplasms.
authors.affiliation: Department of Pathology, Anschutz Medical Campus, University of Colorado at Denver, Denver, Colorado 80045, USA. bk.demasters@ucdenver.edu
authors.forename: Bette Kay
authors.initials: BK
authors.lastname: Kleinschmidt-DeMasters
authors.forename: Ali H
authors.initials: AH
authors.lastname: Alassiri
authors.forename: Diane K
authors.initials: DK
authors.lastname: Birks
authors.forename: Kathy L
authors.initials: KL
authors.lastname: Newell
authors.forename: Wayne
authors.initials: W
authors.lastname: Moore
authors.forename: Kevin O
authors.initials: KO
authors.lastname: Lillehei
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis*; D001932:Brain Neoplasms / Q000737:chemistry / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D002648:Child; D002868:Chromosomal Proteins, Non-Histone / Q000032:analysis*; D002892:Chromosomes, Human, Pair 22; D057167:Claudins; D004268:DNA-Binding Proteins / Q000032:analysis*; D003937:Diagnosis, Differential; D015622:Epithelioid Cells / Q000737:chemistry* / Q000473:pathology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D005909:Glioblastoma / Q000737:chemistry / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D008279:Magnetic Resonance Imaging; D008297:Male; D008565:Membrane Proteins / Q000032:analysis*; D009006:Monosomy; D011237:Predictive Value of Tests; D018335:Rhabdoid Tumor / Q000737:chemistry / Q000175:diagnosis* / Q000235:genetics / Q000473:pathology; D000071796:SMARCB1 Protein; D014157:Transcription Factors / Q000032:analysis*; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; D002868:Chromosomal Proteins, Non-Histone; D057167:Claudins; D004268:DNA-Binding Proteins; D008565:Membrane Proteins; D000071796:SMARCB1 Protein; C513266:SMARCB1 protein, human; D014157:Transcription Factors; C122101:claudin 6