Immunohistochemistry in Clinical Practice

Immunohistochemistry in clinical practice has become the cornerstone of diagnostic pathology. The use of immunohistochemistry continues to grow with increased number of available tests. Immunohistochemistry can confirm the diagnosis and exclude or rule out other entities in the differential diagnosis. It is particularly helpful when used in conjunction with routine morphology and other ancillary techniques. A wide variety of immunohistochemical tests are available to detect CD markers (for hematopoietic proliferations), markers for endothelial and epithelial cells, mesenchymal tissue markers, neural markers, and neuroendocrine markers. Numerous viruses can also be detected with immunohistochemical stains such as herpes simplex viruses, cytomegalovirus, adenovirus, hepatitis B virus, human papilloma virus, Epstein-Barr virus and papoviruses. In fact any protein can be localized to the cytoplasm, cytoplasmic membrane or the nucleus through immunohistochemistry. The division of immunohistochemistry has recently acquired new tests that are becoming important in diagnostic pathology and has hence increased the antibody inventory to>60 tests. These new tests include: 1) C4d. C4d is a stable complement split product of C4 factor of the classic complement pathway that is deposited in the endothelium of capillaries. Detection of C4d deposition is proven a valuable tool for detecting humeral mechanisms of acute rejection in various solid organ transplantations. In the kidney