The thymus: General concepts on embryology, anatomy, histology and immunohistochemistry.

A fundamental aspect that is commonly overlook when assessing thymic tumors is the normal histology and immunohistochemical features of the normal thymus. Given the fact that most epithelial tumors occur in the adult population, it is only rarely that we are confronted with assessing normal immunohistochemistry of the thymus. However, we consider that such knowledge is of utmost importance is assessing pathological conditions including epithelial tumors or tumors of other lineages. Therefore, in this writing we have concentrated our efforts in providing an overview of the embryology and anatomy of the thymus as well as putting the normal histology and immunohistochemistry in perspective when assessing pathological conditions.