Full Description
Until the middle of the present century, the morphology and function of the thymus were primarily of interest to those working in the fields of pathologic anatomy, endo crinology, and pediatrics. However, during recent decades careful and refined histo logic studies of the organ have expanded our knowledge. It now seems certain that the thymus plays a central role in the immune system, and some of the substances pro duced by this organ are considered together under the collective term of "thymic hor mones". In clinical medicine (in particular endocrinology and pediatrics, as well as surgery and radiologic oncology), the startling advances that have taken place in radiologic diagnostics with the advent of new imaging procedures such as computed tomography and magnetic resonance imaging have provided fresh impetus in the search for effec tive treatments for hyperplasia, tumors, and tumor-like changes of the thymus. Normal variants of the thymus, which lies concealed within the anterior superior mediastinum, have been recorded, and pathologic changes such as primary or secondary tumors can now be analyzed and correctly diagnosed.
Contents
1 Introduction — Historical Background.- 2 Anatomy and Embryology of the Thymus.- 2.1 Embryology.- 2.2 Normal Anatomy.- 2.3 Involution.- 3 Immunologic Function of the Thymus.- 3.1 Historical Overview.- 3.2 T Cell Molecules in Antigen Recognition.- 3.3 Ontogeny of T Cells.- 3.4 Cellular Selection in the Thymus.- 3.5 Clinical Aspects.- 3.6 Summary.- 4 Imaging Procedures for Visualization of the Thymus.- 4.1 Plain Film Diagnostics E.Walter and E.Willich.- 4.2 Conventional Tomography.- 4.3 Ultrasonography.- 4.4 Computed Tomography.- 4.5 Magnetic Resonance Imaging W.R.Webb and G.deGeer.- 4.6 Nuclear Medicine E.Walter and E.Willich.- 4.7 Esophagography.- 4.8 Angiography.- 4.9 Obsolete Methods.- 4.10 Supplementary Procedures (Mediastinography, Bronchoscopy, Bronchography) E.Willich.- 5 Diagnostic Imaging of the Normal Thymus.- 5.1 Conventional Diagnostics in Children E.Willich and E.Walter.- 5.2 Ultrasonography.- 5.3 Computed Tomography E.Walter.- 5.4 Magnetic Resonance Imaging W.R.Webb and G.deGeer.- 5.5 Invasive Procedures (Pneumomediastinography, Arteriography, Phlebography) E.Walter.- 5.6 Measurement of the Size of the Thymus E.Willich.- 6 Acute and Stress-Induced Involution of the Thymus.- 6.1 Acute Endogenous Involution of the Thymus.- 6.2 Exogenous Involution of the Thymus: the Steroid Test.- 6.3 Transplacental Influence of Steroids on the Premature Infant's Thymus.- 7 Developmental Abnormalities of the Thymus.- 7.1 Aplasia, Hypoplasia, and Dysplasia E.Willich and E.Walter.- 7.2 Dystopia.- 7.3 Persistent Thymus E.Willich.- 7.4 Hyperplasia.- 8 Tumors of the Thymus.- 8.1 Introduction E.Walter.- 8.2 Epithelial Tumors of the Thymus.- 8.3 Carcinoid Tumors of the Thymus.- 8.4 Thymic Involvement in Malignant Lymphomas and Leukemia E.Willich and E.Walter.- 8.5 MesenchymalTumors (Thymolipoma) E.Walter.- 8.6 Germ Cell Tumors and Teratomas E.Walter.- 8.7 Rare Tumors of the Thymus.- 8.8 Metastases to the Thymus.- 9 Tumor-like (Nonneoplastic) Conditions of the Thymus and/or Mediastinum.- 9.1 Thymogenic Cysts.- 9.2 Hydatidosis of the Thymus.- 9.3 Tuberculoma of the Thymus.- 9.4 Histiocytosis X of the Thymus.- 10 Trauma and Hemorrhage of the Thymus.- 10.1 Trauma.- 10.2 Hemorrhage.- 11 Thymus and Myasthenia Gravis.- 11.1 Definition of Myasthenia Gravis H.Wlethölter.- 11.2 Clinical Manifestation.- 11.3 Associated Thymic Changes.- 11.4 Pathogenesis.- 11.5 Autoimmune Origin.- 11.6 Diagnosis.- 11.7 Treatment H.Wlethölter.
