The Rare Phenomenon of Loss of INI1 Expression at Recurrence/Progression of Primary Central Nervous System Tumors: Report of 3 Cases

Int J Surg Pathol. 2020 May;28(3):341-347. doi: 10.1177/1066896919883942. Epub 2019 Nov 3.


It is extremely rare for loss of immunohistochemical expression of INI1 to occur primarily at recurrence/progression with retained expression at the primary/initial presentation of central nervous system (CNS) tumor. In this article, we present 3 such cases showing loss of INI1 expression primarily at recurrence. All patients were males, aged 7 years (case 1), 11 years (case 2), and 35 years (case 3), diagnosed with low-grade glial/glioneuronal tumor, not otherwise specified (case 1), craniopharyngioma (case 2), and glioblastoma (case 3); all showed retained INI1 protein expression. Case 1 at 12 months recurrence showed a high-grade tumor with relative undifferentiated morphology, case 2 after 104 months showed a sarcomatous progression, and case 3 recurred after 4 months with the presence of relative undifferentiated round cells. All these recurrences showed loss of INI1 expression. Loss of SMARCB1/INI1 gene function resulting in complete loss of INI1 protein expression is not a well-accepted genetic mechanism for transformation/progression as this series emphasizes.

Keywords: AT/RT; INI1 loss; SMARCB1/INI1; recurrent CNS tumors.

Publication types

  • Case Reports

MeSH terms

  • Adult
  • Biomarkers, Tumor / metabolism
  • Brain Neoplasms / pathology*
  • Child
  • Craniopharyngioma / pathology*
  • Disease Progression
  • Fatal Outcome
  • Glioma / pathology*
  • Humans
  • Male
  • Neoplasm Recurrence, Local / pathology*
  • Pituitary Neoplasms / pathology
  • SMARCB1 Protein / biosynthesis*


  • Biomarkers, Tumor
  • SMARCB1 Protein
  • SMARCB1 protein, human