Hassall's corpuscle in thymus (mouse)

Electron microscopy. The centre of a small Hassall's corpuscle consists of darker-stained cells (1) which are keratinizing and represent degenerating cytoplasmic remnants (2). (3) is an infiltrating monocyte and (*) indicate the presence of free keratohyalin granules from disintegrated epithelial cells. Flattened specialized epithelioreticular cells (4) are closely apposing to each other and show desmosomes (-->)