title: The diffuse endocrine system and derived tumours. Histological and histochemical characteristics.
abstract: The Diffuse Endocrine System, to which the so-called APUD (Amine Precursor Uptake and Decarboxylation) cells do belong, gives rise to a group of tumours which may or not secrete amines and/or polypeptide hormones: carcinoids (argentaffinomas, argentaffin or Kultschitzky cell carcinomas). Foregut carcinoids are predominantly of B type (trabecular), argyrophilic, or non-reactive (in about 70% of cases) to silver impregnation. Midgut tumours are generally of A type (insular); more than 80% of them are argentaffinic. Hindgut derived carcinoids are primarily of mixed type; nearly 70% are non-reactive to silver stains. From a cytological standpoint all types may be build up of either small-round, spindle-shaped, polyhedral or cuboidal cells. From a functional point-of-view, the cells are either clear and immature, non-reducing or exhausted. Accordingly, the diagnosis cannot be based alone on silver impregnation or other histochemical methods.
mesh_terms: D001078:APUD Cells / Q000166:cytology*; D001079:Apudoma / Q000473:pathology*; D001943:Breast Neoplasms / Q000473:pathology; D002276:Carcinoid Tumor / Q000473:pathology*; D005260:Female; D005833:Genital Neoplasms, Female / Q000473:pathology; D006801:Humans; D007414:Intestinal Neoplasms / Q000473:pathology; D013194:Staining and Labeling