bromochloroacetic-acid and Cardiovascular-Abnormalities

There were investigated 22 cases from which the thymic tissue was removed either during surgery for cardiovascular malformations (n = 14), or for myasthenia gravis (n = 8). Histological sections were stained with routine morphologic methods, and immunohistochemistry was performed for cytokeratin, CD20, CD3, and S100 protein. Aspects characteristic for thymus involution were found in 11 cases without myasthenia gravis and in all cases with myasthenia gravis. Morphological changes of the thymus of involution are age-dependent. There were characterized stages of involution, with special reference to cortical - medulla inversion, lymphocyte depletion and sequestration. In advanced-stage of involution, epithelial cells are arranged in cords or compact islands, and could mimic a thymoma or a metastatic carcinoma. The immunohistochemical profile is similar but not identical to the active thymus. We noticed a decreased expression of cytokeratin, and a reduced number of CD3, CD20, and S100 positive cells. Morphologic and immunohistochemical peculiarities of the thymus of involution are discussed in relation with the specific pathology of the organ.

Topics: Adolescent; Adult; Antigens, CD20; Atrophy; Carcinoma; Cardiovascular Abnormalities; CD3 Complex; Child; Child, Preschool; Diagnosis, Differential; Humans; Infant; Infant, Newborn; Keratins; Lymphatic Diseases; Middle Aged; Myasthenia Gravis; Thymus Gland; Thymus Neoplasms

The study was conducted on 27 specimens of normal thymus, removed during surgery for cardiovascular malformations. Biopsies were processed using current histological techniques, and the samples were stained using morphological and immunohistochemical methods (cytokeratin profile, vimentin, S100, CD45, CD20, CD3, CD68, CD34 protein, chromogranin A, neuronal-specific enolase, desmin). Microscopic examination focused on the structure and immunohistochemical profile of Hassall corpuscles, beginning from the hypothesis that the epithelial cells of these structures, characteristic for the thymus, participate in the negative and positive selection of thymocytes. Morphological assessment revealed the existence of four different types of Hassall corpuscles: juvenile, immature, mature and senescent. The lymphocyte-rich variant was identified in 25.92% of the cases with ages ranging between 7 days and 12 years. From the immunohistochemical point of view, the following reactions were negative: cytokeratins 7 and 8, vimentin, desmin, CD3, CD68, CD34 and neuron-specific enolase. Isolated positive chromogranin cells were found in two cases, and positive intracorpuscular CD20 cells in one case. Polyclonal cytokeratins were positive in all instances in the epithelial cells of the Hassall corpuscles, with higher intensity in high-molecular weight cytokeratin, strongly expressed in mature corpuscles. All specimens had positive S100 cells in the corpuscles, distributed among the epithelial cells, with dendritic morphology, in great numbers in juvenile and immature forms. Morphological and immunohistochemical results (corpuscle variants, the presence of positive S100 cells, concentration of positive CD20 and CD3 cells around the corpuscles) suggest the active involvement of epithelial cells of Hassall corpuscles in modulating the differentiation of thymocytes at the medullar level, a process that is mediated by protein S100 positive corpuscular dendritic cells.

Topics: Antigens, CD; Biopsy; Cardiovascular Abnormalities; Epithelial Cells; Humans; Infant, Newborn; Keratins; Reference Values; Thymectomy; Thymus Gland