A Dermatopathologist's Guide to Troubleshooting Immunohistochemistry--Part 2: Troubleshooting Immunohistochemical Tests in the Laboratory.

Unexpected staining patterns can arise from problems occurring in any of the steps required for IHC, some of which are discussed in part I of this CME series. Whether used to differentiate benign from malignant tumors, identify tumor subtypes, subtypes of hematopoietic malignancies, or identifying targets for therapy, the pathologist must be intimately familiar with the potential pitfalls that are inherent in the IHC methodology to troubleshoot problems in the laboratory, and more importantly, when interpreting immunohistochemical staining, to avoid pitfalls of false-positive or false-negative stains.