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  • Absence of nuclear INI-1 expression in malignant extra-renal rhabdoid tumor (MERT). The background lymphocytes and endothelial cells serve as a positive internal control.
  • Absence of nuclear INI-1 expression in malignant extra-renal rhabdoid tumor (MERT). The background lymphocytes and endothelial cells serve as a positive internal control.
  • Loss of nuclear INI-1 expression in malignant extra-renal rhabdoid tumor (MERT). Note the background non-tumor cells are positive (normal).
  • Loss of nuclear INI-1 expression in malignant extra-renal rhabdoid tumor (MERT). Note the background non-tumor cells are positive (normal).

INI-1 (integrase interactor 1) is a tumor suppressor gene[1] that is constitutively expressed in most normal cells in the body. It is mutated resulting in loss of expression in malignant rhabdoid tumors and epithelioid sarcomas.

SynonymsEdit

  • SMARCB1
  • INI1
  • Integrase Interactor 1
  • hSNF5[1]

AntibodiesEdit

Technical InfoEdit

Staining PatternEdit

  • INI-1 is a nuclear antigen that is normally expressed in essentially all nucleated cells. Thus, a significant INI-1 stain result will show LOSS of nuclear INI-1 staining. To interpret this stain and ensure that it worked correctly, you MUST see nuclear staining on other normal/non-neoplastic cells on the slide. Without an appropriate internal control of INI-1 expression in these normal cells, one cannot be certain that the INI-1 immunostain actually worked.

Expression in Normal TissuesEdit

Expression in Neoplastic EntitiesEdit

LOSS of INI-1 nuclear staining is seen in the following:

BenignEdit
Tumor name % Positive Staining (Sensitivity) Number of Cases Specificity Comments


MalignantEdit
Tumor name % Positive Staining (Sensitivity) Number of Cases Specificity Comments
Epithelioid Sarcoma 79%[2] 19/24[2]
Epithelioid Sarcoma, proximal type*
Malignant Extrarenal Rhabdoid Tumor* 100%[3] 15/15[3]
Rhabdoid Tumors of Kidney 100%[3] 29/29[3]
Atypical Teratoid/Rhabdoid Tumor (ATRT) of CNS 100%[4] 20/20[4]

.* Some authors consider these to be two different names describing the same tumor. Others believe they are separate entities.

Expression in Non-Neoplastic EntitiesEdit

Practical Uses / PanelsEdit

Common PitfallsEdit

  • INI-1 normally is "positive" (ie - stains) the nuclei of almost all normal cells. Negativity for, or LOSS of, INI-1 is the only significant finding.
  • INI-1 should only be interpreted in a tumor when the background tissue shows positive nuclear staining in normal cells.

ReferencesEdit

  1. 1.0 1.1 The EMBO Journal (2002) 21, 31 - 42 doi:10.1093/emboj/21.1.31
  2. 2.0 2.1 Am J Dermatopathol. 2009 Apr;31(2):152-6.
  3. 3.0 3.1 3.2 3.3 Am J Surg Pathol. 2004 Nov;28(11):1485-91.
  4. 4.0 4.1 Am J Surg Pathol. 2004 May;28(5):644-50.

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