title: Papillary glioneuronal tumor--a rare entity: report of four cases and brief review of literature.
abstract: OBJECTIVE
  Papillary glioneuronal tumors (PGNT) have been recently included as a distinct entity in the WHO classification of tumors of the central nervous system. Their molecular pathogenesis is not clear. In the current study, we present the morphological, immunohistochemical, and molecular features of four cases of PGNT reported over the past 11 years.
  
  
  METHODS
  Over a period of 11 years (January 2000-February 2010), there were four cases of PGNT, which were reviewed for histomorphological features. TP53 and IDH1 mutations were assessed using antibodies against p53 protein and for mutant IDH1(R132H) protein, respectively. Immunohistochemistry was also performed for epidermal growth factor receptor (EGFR) protein. Fluorescence in situ hybridization assay was used for analyzing 1p/19q deletion status.
  
  
  RESULTS
  All the tumors showed the characteristic biphasic morphology. Rare findings included minigemistocyte-like cells in one, angiomatous areas in three, focal necrosis in one, and a high MIB-1 labeling index of 12 and 13 %, respectively, in two of the cases. All lacked EGFR, IDH1 expression, and 1p/19q deletions. Interestingly, antibody for p53 labeled the tumor cells, mainly those showing glial differentiation, in two cases. At a mean follow-up of 30 months, there was no evidence of disease progression except in one case which recurred after 24 months.
  
  
  CONCLUSIONS
  PGNT are rare CNS neoplasms. Despite showing focal morphological features reminiscent of oligodendroglial tumors and presence of astrocytic component, they usually lack the common genetic alterations involved in the pathogenesis of gliomas. Multi-institutional pooling of cases may aid in elucidating their oncogenetic pathway.
authors.affiliation: Departments of Pathology, All India Institute of Medical Sciences (AIIMS), New Delhi 110029, India.
authors.forename: Shipra
authors.initials: S
authors.lastname: Agarwal
authors.forename: Mehar Chand
authors.initials: MC
authors.lastname: Sharma
authors.forename: Geetika
authors.initials: G
authors.lastname: Singh
authors.forename: Vaishali
authors.initials: V
authors.lastname: Suri
authors.forename: Chitra
authors.initials: C
authors.lastname: Sarkar
authors.forename: Ajay
authors.initials: A
authors.lastname: Garg
authors.forename: Rajinder
authors.initials: R
authors.lastname: Kumar
authors.forename: P Sharat
authors.initials: PS
authors.lastname: Chandra
mesh_terms: D000293:Adolescent; D000328:Adult; D001932:Brain Neoplasms / Q000378:metabolism* / Q000473:pathology*; D002648:Child; D002675:Child, Preschool; D066246:ErbB Receptors / Q000235:genetics / Q000378:metabolism; D005260:Female; D006801:Humans; D007521:Isocitrate Dehydrogenase / Q000235:genetics / Q000378:metabolism; D008279:Magnetic Resonance Imaging; D008297:Male; D009154:Mutation / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000378:metabolism; D009837:Oligodendroglioma / Q000378:metabolism* / Q000473:pathology*; D012189:Retrospective Studies; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
chemical_list: D009419:Nerve Tissue Proteins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D007521:Isocitrate Dehydrogenase; C543588:IDH1 protein, human; C512478:EGFR protein, human; D066246:ErbB Receptors