title: The first histological and immunohistochemical examination of thymus in a case of fetus in fetu.
abstract: Fetus in fetu (FIF) is a rare condition with less than 150 cases reported in the world to the best of our knowledge. It is a malformed monozygotic twin ("non-dominant twin"), which is found inside the body of a living child or sometimes in an adult ("dominant twin"). Different organs can be seen in these fetuses; vertebral column limbs, central nervous system, gastrointestinal tract, vessels, and genitourinary tract. In the literature, we found only two cases of fetus in fetu with the present thymic tissue. In this paper, the thymus of non-dominant twin exteriorized from the mediastini of dominant twin, was analyzed by histological and imunohistochemical methods. Even though the majority of organs did not develop normally in the mentioned case, thymic tissue was proved to be present in many body parts of the non-dominant twin. In spite of the fact that the cortex and the medulla were not so distinguishable as in the normal thymuses, presence of many basic cell populations was demonstrated: thymic epithelial cells (AE1/AE3 positive cells), T (CD45RO positive) and B (CD20 positive) cells, macrophages (CD68 positive cells), dendritic cells (S100 positive cells) and myoid cells (desmin positive). The Hassall's bodies were localized mostly in the medulla, however in sporadic cases they occurred in the area close to the connective tissue septa. The superficial epithelial cells of the Hassall's corpuscules as well as their internal contents, were markedly stained by alcian blue, and the cystic formations, found inside the Hassall's bodies, contained PAS-positive substance, similar to Hassall's bodies of normal thymuses. This fact indicates that although development of the parasitic twin is incomplete, all three germ layers participate on its development.
authors.affiliation: Department of Histology and Embryology, Comenius University in Bratislava, Slovakia. ivan.varga@fmed.uniba.sk
authors.forename: Ivan
authors.initials: I
authors.lastname: Varga
authors.forename: Veronika
authors.initials: V
authors.lastname: Jablonska
authors.forename: Vladimir
authors.initials: V
authors.lastname: Cingel
authors.forename: Eliska
authors.initials: E
authors.lastname: Kubikova
authors.forename: Frantisek
authors.initials: F
authors.lastname: Dorko
authors.forename: Stefan
authors.initials: S
authors.lastname: Polak
mesh_terms: D015703:Antigens, CD / Q000032:analysis; D015214:Antigens, Differentiation, Myelomonocytic / Q000032:analysis; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology; D003713:Dendritic Cells / Q000166:cytology / Q000276:immunology; D004847:Epithelial Cells / Q000166:cytology; D005333:Fetus / Q000002:abnormalities*; D006801:Humans; D007150:Immunohistochemistry; D007231:Infant, Newborn; D008264:Macrophages / Q000166:cytology / Q000276:immunology; D008297:Male; D009418:S100 Proteins / Q000032:analysis; D013601:T-Lymphocytes / Q000166:cytology / Q000276:immunology; D013950:Thymus Gland / Q000002:abnormalities / Q000166:cytology / Q000196:embryology* / Q000276:immunology; D014430:Twins, Monozygotic; D000097382:CD68 Molecule
chemical_list: D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D009418:S100 Proteins; C067980:CD68 antigen, human; D000097382:CD68 Molecule