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.
Synonyms[]
- SMARCB1
- INI1
- Integrase Interactor 1
- hSNF5[1]
Antibodies[]
Technical Info[]
Staining Pattern[]
- 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 Tissues[]
Expression in Neoplastic Entities[]
LOSS of INI-1 nuclear staining is seen in the following:
Benign[]
Tumor name | % Positive Staining (Sensitivity) | Number of Cases | Specificity | Comments |
Malignant[]
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 Entities[]
Practical Uses / Panels[]
Common Pitfalls[]
- 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.