INI1/RCB1/|BAF47 tumour suppressor gene

The gene variously known as hSNF/INI1/SMARCB1/BAF47 is a putative tumour suppressor gene located on chromosome 22q11.2. It is a member of the SWI/SWF chromatin-remodelling complex and is normally expressed in all tissues.

Staining is nuclear. An antibody reactive with the gene product in formalin-fixed paraffin-embedded tissues is available. Inactivation of the gene occurs in most malignant rhabdoid tumours including paediatric CNS atypical teratoid/rhabdoid tumours, and loss of staining is potentially diagnostically useful. INI1 mutation does not appear to result in cytoplasmic accumulation of the protein. Negativity occurs even in those malignant rhabdoid tumours in which there is no INI1 deletion or mutation: the mechanism in these cases is not known.

Immunoreactivity

Normal endothelial and haematogenous cell nuclei are immunoreactive3.

 

Renal rhabdoid tumour

0/291

  

Extra-renal rhabdoid tumour

0/151

CNS atypical teratoid/rhabdoid tumour

0/202, 0/173, 0/13

Ewing's sarcoma

13/131

CNS PNET

10/102

Alveolar rhabdomyosarcoma

3/31

Embryonal rhabdomyosarcoma

2/21

DSRCT

5/51

Renal clear cell sarcoma

4/41

Wilm's tumour

6/61

Undifferentiated sarcoma

2/21

Cellular congenital mesoblastic nephroma

4/41

Epithelioid sarcoma†

2/21

Synovial sarcoma

4/4 focal1

Childhood choroid plexus carcinoma

5/52, 2/23, 21/284

Childhood craniopharyngeoma

2/22

Childhood ependymoma

2/22

Childhood anaplastic ependymoma

27/273

Childhood oligodendroglioma

1/22

Childhood anaplastic oligodendroglioma

1/13

Childhood astrocytoma

2/22

Childhood CNS ganglioglioma

2/22

Childhood mixed anaplastic oligoastrocytoma

1/1, focal2

Childhood glioblastoma multiforme

2/22

Childhood glioblastoma

41/413

Childhood pilocytic astrocytoma

2/22

Childhood anaplastic astrocytoma

6/63

Childhood pituitary adenoma

equivocal in one case2

Childhood CNS germ cell tumour

2/22

Childhood medulloblastoma

  

classic

115/1213

nodular / desmoplastic

17/173

large cell / anaplastic

20/203

total

152/1583

Childhood supratentorial PNET

25/273

Childhood medulloepithelioma

1/13

Childhood germ cell tumour

8/83
Ossifying fibromyxoid tumour of soft parts
retained mosaic loss in 30%-60% of cells
5/195 14/195
 
   
   

†Epithelioid sarcoma, like CNS atypical teratoid/rhabdoid tumour, commonly shows loss of alleles from chromosome 22.

Paediatric CNS tumours negative for INI1 tend to show an aggressive course even if they appear to lack rhabdoid features; they may represent cases of CNS atypical teratoid/rhabdoid tumour3.

References

1 Hoot, A. C., P. Russo, et al. (2004). "Immunohistochemical analysis of hSNF5/INI1 distinguishes renal and extra-renal malignant rhabdoid tumors from other pediatric soft tissue tumors." Am J Surg Pathol 28(11): 1485-91.

2 Judkins, A. R., J. Mauger, et al. (2004). "Immunohistochemical analysis of hSNF5/INI1 in pediatric CNS neoplasms." Am J Surg Pathol 28(5): 644-50.

3 Haberler C, Laggner U, Slavc I, et al. Immunohistochemical analysis of INI1 protein in malignant pediatric CNS tumors: Lack of INI1 in atypical teratoid/rhabdoid tumors and in a fraction of primitive neuroectodermal tumors without rhabdoid phenotype. Am J Surg Pathol 2006; 30:1462-8

4 Judkins AR, Burger PC, Hamilton RL, et al. INI1 protein expression distinguishes atypical teratoid/rhabdoid tumor from choroid plexus carcinoma. J Neuropathol Exp Neurol 2005; 64:391-7

5 Graham RP, Dry S, Li X, Binder S, Bahrami A, Raimondi SC, et al. Ossifying fibromyxoid tumor of soft parts: a clinicopathologic, proteomic, and genomic study. Am J Surg Pathol. 2011 Nov;35(11):1615-25.

 

This page last revised 19.10.2011.

©SMUHT/PW Bishop