Immunohistochemistry, or IHC, is an essential method used in cancer diagnosis that involves labelling specific antigens in tissue samples using antibodies. This technique can help identify cancer cells and tissues, as well as determine the tumor's characteristics, progression, and prognosis. Among the various markers used in IHC, there are some commonly used ones that have significant diagnostic value.

Cytokeratin

Cytokeratin is a protein found in cells' cytoplasm and is used as a marker for epithelial cells. Epithelial cells form the lining of various organs and are vital in assessing cancer cells. In cancer diagnosis, cytokeratin is a crucial marker in distinguishing carcinomas from other cancer types, such as mesenchymal tumors, which mainly comprise connective tissue cells. A positive cytokeratin IHC test result indicates epithelial cell origin and can help guide further diagnostic and therapeutic decisions.

HER2

The human epidermal growth factor receptor 2 (HER2) is a protein that plays a critical role in cell growth and division. Its overexpression is commonly found in certain types of cancer, especially breast cancer. HER2 positivity is indicative of aggressive cancer characteristics and poor prognosis; thus, it is important in determining treatment options. HER2-targeted therapies, such as Trastuzumab, have made significant improvements in treating HER2-positive breast cancer.

CD20

CD20 is a protein found in normal B-cells, which are responsible for the body's humoral immunity. In cancer diagnosis, CD20 expression is predominantly used in determining the type of lymphomas, such as B-cell lymphomas. This marker's identification helps distinguish B-cell lymphomas from T-cell lymphomas and other lymphoproliferative disorders, which can affect treatment outcomes. Additionally, CD20-targeted therapies, such as Rituximab, have shown efficacy in treating CD20-positive lymphomas.

Ki-67

Ki-67 is a protein found in the nucleus of dividing cells and is essential in cell proliferation. In cancer diagnosis, Ki-67 is used to assess the tumor's growth rate and aggressiveness. A high Ki-67 expression is indicative of fast-growing tumors; thus, it can aid in determining the prognosis and guiding treatment options.

p53

The p53 protein plays a crucial role in regulating cell division and preventing cell mutations. Mutations in the p53 gene are commonly found in various cancer types, such as lung and colon cancer. In cancer diagnosis, detecting p53 mutations via IHC can aid in determining specific cancer types and assessing the tumor's aggressiveness. Additionally, p53-targeted therapies, such as PRIMA-1, have shown promise in treating p53-mutant tumors.

Conclusion

In conclusion, IHC markers play a critical role in cancer diagnosis, aiding in identifying specific cancer types, assessing their characteristics, and guiding treatment options. Cytokeratin, HER2, CD20, Ki-67, and p53 are some commonly used IHC markers in cancer diagnosis, and their significance lies in distinguishing cancer cells from normal ones and assessing their growth rate, aggressiveness and identifying mutations. By understanding common IHC markers' significance, healthcare professionals can make informed diagnostic and therapeutic decisions, ultimately leading to better patient outcomes.