Thymoma is characterized by various clinical manifestations. About half of them are manifested as an asymptomatic course, others occur in a combination with different syndromes. 25% of patients develop compression of tumor blood vessels, nerves and organs of the mediastinum or clinical signs of germination of thymic tumor in other organs. 40% of patients are diagnosed with autoimmune diseases due to dysfunction of the thymus. Generalized myasthenia gravis (75%) is most frequently observed.
The objective of the research was to study clinical and immunological peculiarities of myasthenia gravis depending on the size and histological type of thymoma.
Materials and methods. The results of clinical and immunological, instrumental and histological examination of 30 patients with myasthenia on the background of thymoma were analyzed. The severity of the disease was assessed using clinical classification of the Myasthenia Gravis Foundation of America (MGFA, 2001).To determine the barrier function of phagocytic cells, phagocytosis activity of neutrophils was evaluated using the light microscope. The phagocytic index, the phagocytic number and the index of phagocytosis completion were determined. The suspension culture of Saccharomyces cerevisiae was used as a microbial agent. Preparations were stained using the Romanovsky-Himze methods. Neutrophilic leukocytes were separated from leukocyte suspension of peripheral blood. The expression of differentiation clusters CD3+, CD4+ and CD8+ on subpopulation of T- and B-cells were evaluated by indirect ELISA using monoclonal antibodies labeled with FITC-dye. To diagnose thymoma, we used spiral CT “Marconi” SeleCT/SP. For histologic study thymoma samples were fixed in 10% neutral formalin for 24 hours. The material was embedded in paraffin after posting through the chloroform in the usual way; then, sections with the thickness of 5-7 μm were prepared. Preparations were stained with hematoxylin and eosin.
Results and conclusions. The severity of the clinical course of myasthenic syndrome on the background of thymoma does not depend on tumor size; it depends on the histologic type and immunological imbalance. The severest clinical picture was observed in patients with type AB thymoma and the least severe course of myasthenic symptoms was found in patients with lymphoid thymoma (type B1). Lymphoepithelial and epithelial thymomas were accompanied by similar immunological disorders. The reduction in the levels of CD3+ and CD4+ lymphocyte subpopulations can be used as a reliable diagnostic criterion. Lymphoid thymomas are characterized by a significant reduction in the indicators of the phagocytic index, the phagocytic number, and the level of CD8+ lymphocyte subpopulations as well as an increase in the level of CD4+ subpopulations. Surgical treatment as a method of choice in case of radical immunosuppression is indicated for all patients with confirmed thymoma regardless of its size and histological characteristics.
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