Malignant Extra-Renal Rhabdoid Tumor : Loss of INI1 Expression

Comments:
Almost all rhabdoid tumors (renal, extrarenal, and atypical rhabdoid/teratoid tumor of CNS) show complete loss of normal nuclear expression of INI1 protein by immunohistochemistry. Most of these cases show biallelic inactivation of SMARCB1 by deletions and/or mutations. However, about 20% of rhabdoid tumors with loss of INI1 expression have no evidence of SMARCB1 gene alterations.

The image shows complete lack of nuclear staining for INI1 in the tumor cells. The preserved expression in the stromal cells and renal tubular epithelium (lower right) serves as internal positive control. Image courtesy of Dr. Jean-Christophe Fournet, Paris, France; humpath.com; Used with permission