Immunohistochemistry of INI1 expression: a new tool for old challenges in CNS and soft tissue pathology.

Immunohistochemical staining for INI1 (BAF47) expression has been recently described. Loss of expression of INI1 as detected by immunohistochemical staining correlates with deletion and mutations of the INI1 gene in patients with malignant rhabdoid tumors and central nervous system atypical teratoid/rhabdoid tumors and as such is a sensitive and specific marker for these tumors. Loss of INI1 expression may rarely be encountered in other tumor types. This article reviews the utility of immunohistochemical staining for INI1 expression.