title: INI1 protein expression distinguishes atypical teratoid/rhabdoid tumor from choroid plexus carcinoma.
abstract: Central nervous system atypical teratoid/rhabdoid tumor (AT/RT) and choroid plexus carcinoma (CPC) are rare, highly malignant tumors that predominantly arise in infants and young children. Overlapping clinical, histologic, ultrastructural, or immunophenotypic features may obscure the diagnosis in some cases. AT/RT is characterized by deletions and/or mutations of the INI1 tumor-suppressor gene on chromosome band 22q11.2. We have recently developed an INI1 immunohistochemical staining assay. Negative staining of tumor cells resulting from inactivation of the INI1 gene is a consistent feature of AT/RT. Mutations of INI1 in some CPCs have been reported. The purpose of the present study was to determine if immunohistochemical staining with an INI1 antibody would provide a sensitive means of distinguishing between CPC and AT/RT. We examined 28 tumors with a submitted diagnosis of CPC. Twenty-one CPCs showed retained expression of INI1 and seven tumors showed loss of INI1 expression. Cytogenetic, FISH, and/or INI1 mutation results were also available for 13 tumors. In three of the seven cases, monosomy 22 was the only cytogenetic abnormality, suggestive of AT/RT. However, monosomy 22 was also identified in 3 tumors with complex karyotypes that retained INI1 expression. The 7 tumors that were immunonegative for INI1 had features that were consistent with AT/RT. Immunostaining for INI1 protein is retained in the majority of CPC and is lost in AT/RT. This expression pattern seems to better define the 2 groups of tumors than does light or electron microscopy, routine immunohistochemistry, or cytogenetic analysis alone.
authors.affiliation: Department of Pathology, University of Pennsylvania School of Medicine and Children's Hospital of Philadelphia, 3615 Civic Center Blvd., Philadelphia, PA 19104, USA.
authors.forename: Alexander R
authors.initials: AR
authors.lastname: Judkins
authors.forename: Peter C
authors.initials: PC
authors.lastname: Burger
authors.forename: Ronald L
authors.initials: RL
authors.lastname: Hamilton
authors.forename: Bette
authors.initials: B
authors.lastname: Kleinschmidt-DeMasters
authors.forename: Arie
authors.initials: A
authors.lastname: Perry
authors.forename: Scott L
authors.initials: SL
authors.lastname: Pomeroy
authors.forename: Marc K
authors.initials: MK
authors.lastname: Rosenblum
authors.forename: Anthony T
authors.initials: AT
authors.lastname: Yachnis
authors.forename: Holly
authors.initials: H
authors.lastname: Zhou
authors.forename: Lucy B
authors.initials: LB
authors.lastname: Rorke
authors.forename: Jaclyn A
authors.initials: JA
authors.lastname: Biegel
mesh_terms: D000293:Adolescent; D017209:Apoptosis; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism*; D002277:Carcinoma / Q000378:metabolism* / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D016545:Choroid Plexus Neoplasms / Q000378:metabolism* / Q000473:pathology; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D017403:In Situ Hybridization / Q000379:methods; D007223:Infant; D008297:Male; D018396:Mucin-1 / Q000378:metabolism; D000071796:SMARCB1 Protein; D013194:Staining and Labeling / Q000379:methods; D013724:Teratoma / Q000378:metabolism* / Q000473:pathology; D014157:Transcription Factors
chemical_list: D014408:Biomarkers, Tumor; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D018396:Mucin-1; D000071796:SMARCB1 Protein; C513266:SMARCB1 protein, human; D014157:Transcription Factors