I work with many GI biopsies and occassionally we send off slides for testing for MSI (Microsattelite Instability). This is a test for Hereditary Nonpolyposis Colorectal Cancer (HNPCC), also known as Lynch Sydrome. The IHC tests for normal gene expression. You can "google" HNPCC or MSI and find several informative sites.
Hope this helps,
Shelly