Corpuscles in thymus (human, puberty)

Stain: Hematoxylin. A: Several thymic (Hassall's) corpuscles (*) of varying sizes within the medulla (1). The Hassall bodies are surrounded by recognizable flattened cells showing keratohyalin granules. The outer shell consists of more layers of close packed concentrically arranged cells with light-stained nuclei characteristic for these specialized epithelioreticular cells (3, -->). The small cells with dark nuclei are thymocytes or T cells. Light-stained epithelial reticular cells (4, -->) form the cytoreticulum of the organ. (2) indicates a small blood vessel.