Four new cases of ectopic hamartomatous thymoma are presented. The tumor occurred either superficially or deep in the area of the sternoclavicular joint and consisted of solid islands of squamous epithelium which blended with spindled cells. Cysts lined by squamous epithelium, small glands, and fat also occurred in variable amounts. Both the spindled and epithelial regions of the tumor expresse...

At imaging, the thymus appears in a variety of shapes and sizes, even in the same individual. It gradually involutes with age and may acutely shrink during periods of bodily stress. During the recovery period, it grows back to its original size or even larger, a phenomenon known as thymic rebound hyperplasia. These anatomic variations and dynamic changes appear to be the main source of confusio...

The thymus has spatially distinct microenvironments, the cortex and the medulla, where the developing T-cells are selected to mature or die through the interaction with thymic stromal cells. To establish the immunological self in the thymus, medullary thymic epithelial cells (mTECs) express diverse sets of tissue-specific self-antigens (TSAs). This ectopic expression of TSAs largely depends on ...

Myasthenia gravis (MG) is an autoimmune disease mediated by autoantibodies against the acetylcholine receptor (AChR) at the neuromuscular junction. MG symptoms are characterized by muscle weaknesses. The thymus of MG patients is very often abnormal and possesses all the characteristics of tertiary lymphoid organs such as neoangiogenesis processes, overexpression of inflammatory cytokines and ch...

Myasthenia gravis (MG) is an autoimmune disease mainly caused by antiacetylcholine receptor autoantibodies (seropositive (SP) disease) or by Abs against unknown autoantigenic target(s) (seronegative (SN) disease). Thymectomy is usually beneficial although thymic hyperplasia with ectopic germinal centers is mainly observed in SP MG. To understand the role of thymus in the disease process, we com...

The ternary complex factors (TCFs; SAP-1, Elk-1, and Net) are serum response factor cofactors that share many functional properties and are coexpressed in many tissues. SAP-1, the predominant thymus TCF, is required for thymocyte positive selection. In this study, we assessed whether the different TCFs are functionally equivalent. Elk-1 deletion, but not the hypomorphic Net(delta) mutation, exa...

A 38-year-old man was admitted for evaluation of Cushing's syndrome. Physical findings showed swelling of the face, and hypertension, but not Cushingoid stigmata. Laboratory data revealed serum cortisol level of 34.1 µg/dL and plasma ACTH of 140 pg/mL. Overnight administration of 1 and 8 mg dexamethasone did not suppress plasma ACTH or serum cortisol. Chest X-ray showed a mass at the upper-ante...

The immune system has evolved mechanisms to recognize and eliminate threats, as well as to protect against self-destruction. Tolerance to self-antigens is generated through two fundamental mechanisms: (a) elimination of self-reactive cells in the thymus during selection and (b) generation of a variety of peripheral regulatory cells to control self-reactive cells that escape the thymus. It is be...

Both humans and mice with a mutation in the autoimmune regulator (aire) gene develop multiorgan autoimmune disease. Aire was shown to exert its critical function in medullary epithelial cells of the thymus by promoting ectopic expression of peripheral tissue antigens. It was hypothesized that the widespread autoimmunity of Aire-deficient individuals reflects a lack of tolerance induction to the...