Immunohistochemistry and in-situ hybridization

In some situations, it is not enough to look through a microscope to determine the diagnosis. For a qualified doctor, such indicators as the absence or presence of protein are important in order to start targeted therapy; hormonal susceptibility of a tissue or organ; molecular confirmation of the type of tissue, including in oncology, where the type of tissue from which the tumor grows is of fundamental importance for treatment. In such situations, traditional histology is no longer sufficient, and methods of molecular biology are used.

Initially, along with histology, histochemistry appeared, a branch of histology that closely interacts with chemistry. This is due to the fact that some kind of chemical reaction was carried out directly on the histological material, and the reagents for the reaction were selected in such a way that they would stain when reacting with tissue molecules (in the section). In this way, it is possible to witness the presence of certain molecules in the tissue, and this may be a confirmation of a disease.

One of the widely used methods is immunohistochemistry, in which proteins are detected in the histological material (slice). Immunohistochemistry appeared in the middle of the twentieth century, but for a long time remained the domain of scientific laboratories, since the molecular features of cells did not matter for the treatment methods that existed at that time. At the end of the twentieth century, targeted therapy entered the arena, and the identification of certain types of proteins became crucial for prescribing treatment: patients with seemingly the same disease began to be treated in different ways. This has led to the fact that immunohistochemistry has now become a reality for any self-respecting large histological laboratory.

Another widespread molecular method has become in situ-hybridization (lit. "in situ hybridization"), which is somewhat similar to immunohistochemistry, but it is not proteins that are detected, but genes. This method is relatively young and its role is likely to expand significantly in the future, but now its use is limited only to certain types of tumors, including breast cancer.