Pharyngeal tonsil ('gut-associated lymphatic tissue' or GALT) (human)

Stain: Azan. The combination demonstrates stages of infiltration (=diapedesis) of lymphocytes in the epithelium of the pharyngeal tonsil. The pharyngeal tonsil or adenoid is located in the nasopharyngeal roof. The agglomerations of lymphocytes (4) are covered by (1) pseudostratified ciliated epithelium with goblet cells (2) included. Locally islands of multilayered squamous epithelium occur (A5), B3 indicate extended layering (local metaplasia). The epithelium is usually infiltrated with lymphocytes (black arrows-->), what may cause desquamation (3) of the epithelium. The blue arrows (C) indicate antigen-presenting cells (APC's) which show a large pale nucleus and a conspicuous nucleolus. The surface is enlarged by microfolds (A). Strands of connective tissue are stained blue and continue in a fine reticular tissue between the lymphocytes