Klin Onkol 2022; 35(1): 20-31. DOI: 10.48095/ccko202220.
Background: IgG4 is the least represented subclass of human imunnoglobulines G (IgG) in serum and differs from other antibodies by its unique biological properties. Although its function in the immune response is not entirely clear, it is mainly involved in the regulation of the immune response. It is formed as a result of chronic or strong antigenic stimulation; in such a case, it becomes a predominantly formed IgG subclass. IgG4 play a key role in the immune tolerance in allergies and tumors. The tolerogenic potential of IgG4 is used in the treatment of allergic diseases using the allergen immunotherapy; at the same time, it is also involved in inducing the immunological tolerance in the microenvironment of tumors, which promotes tumor progression. The increase of serum IgG4 is associated with relatively recently described groups of diseases. In addition to the IgG4-autoimmune diseases, it is mainly connected with IgG4-associated diseases (IgG4-RD) where various organs of the human body are affected by the formation of fibrous and sclerosing deposits in this group of the immune-mediated diseases, which leads to specific organ dysfunction. The most commonly affected organs include the pancreas and large salivary glands; moreover, the orbits and lacrimal glands, the biliary tract, the lungs, the kidneys, the retroperitoneum, the aorta, the meninges, and the thyroid gland may also be affected. It is not entirely clear whether these patients have a higher prevalence of cancer than the general population; however, there is also another relationship between IgG4 and cancer. IgG4-RD very often imitate advanced cancer in medical imaging techniques, so its existence should also be considered in the differential diagnosis of malignancies. Purpose: The aim of this article is to draw attention of clinical oncologists to the issue of IgG4-associated diseases group which can mimic cancer condition in various organs in the human body. Therefore, it is necessary to bear them in mind in the differential diagnosis of malignant diseases.
