Immunohistochemistry and gastrointestinal carcinomas

In the past 25 years, the technique of immunohistochemistry has become a near-routine procedure in the assessment of many malignancies involving the GI tract. This technique is useful in various determinations, not the least of which is the origin of a malignancy in the setting of metastatic disease. The following is an effort to summarize the more useful aspects of that collective knowledge.