Stains & molecular markers
INI1 / SMARCB1
Copyright: 2002-2021, PathologyOutlines.com, Inc.
PubMed Search: INI1[TI]
INI1 / SMARCB1
Author: Lauren N. Stuart, M.D., M.B.A.
Topic Completed: 1 May 2013
Minor changes: 9 October 2020
Copyright: 2002-2021, PathologyOutlines.com, Inc.
PubMed Search: INI1[TI]
Table of Contents
Definition / general | Clinical features | Uses by pathologists | Microscopic (histologic) images | Positive staining - normal | Positive staining - disease | Negative stainingCite this page: Stuart L. INI1 / SMARCB1. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/stainsini1.html. Accessed January 16th, 2021.
Definition / general
- Expressed in all cell types; involved in chromatin remodeling and transcriptional regulation (Histopathology 2012;61:1245)
- Also called hSNF5, SMARCB1 and BAF47
Clinical features
- Chromatin remodeling protein which represses Aurora A, required for rhabdoid tumor cell survival (Cancer Res 2011;71:3225)
- Also represses basal HIV1 promoter activity (J Gen Virol 2009;90:2503)
- Loss of INI1 expression usually associated with deletion or mutation of the INI1 gene on 22q11.2, but not always (Am J Surg Pathol 2012;36:128)
- Germline INI1 mutations associated with sporadic schwannomatosis (10% of cases, BMC Neurol 2011;11:9), rhabdoid tumors (35%, Clin Cancer Res 2011;17:31)
- Interpretation: nuclear stain
Uses by pathologists
- Diagnosis of CNS atypical teratoid / rhabdoid tumors, renal medullary carcinoma and rhabdoid tumors (loss of expression)
- Distinguish atypical teratoid / rhabdoid tumor (loss of INI1) from choroid plexus carcinoma (INI1+, J Neuropathol Exp Neurol 2005;64:391)
- Differentiate epithelioid sarcoma (loss of INI1) from epithelioid hemangioendothelioma (INI1+, Am J Surg Pathol 2009;33:542)
Microscopic (histologic) images
Images hosted on other servers:
Composite rhabdoid tumors
Epithelioid sarcoma (INI1-)
Synovial sarcoma
With rhabdoid features
Positive staining - normal
- Most normal cells
Positive staining - disease
- Composite rhabdoid tumors, including rhabdoid meningioma (Mod Pathol 2005;18:951), synovial sarcoma (but reduced levels in 65%, Mod Pathol 2010;23:981)
- Renal cell carcinoma or urothelial carcinoma, including those with histological rhabdoid features
- Retained expression in epithelioid sarcoma-like hemangioendothelioma
Negative staining
- Loss of INI1 expression found in CNS atypical teratoid / rhabdoid tumor (Am J Surg Pathol 2004;28:644), epithelioid MPNST (50%) and epithelioid sarcoma (Am J Surg Pathol 2009;33:542, Am J Clin Pathol 2009;131:222)
- Also extraskeletal myxoid chondrosarcomas (15%, Am J Surg Pathol 2008;32:1168), myoepithelial carcinoma (occasional), renal medullary carcinoma (Mod Pathol 2008;21:647) and renal rhabdoid tumor (pediatric and adult)
