NUCLEOLAR ORGANIZER REGIONS IN PATHOLOGY

Traditional approaches to pathological diagnosis include macroscopic examination and formalin fixation with the preparation of paraffin sections stained with a variety of histo- chemical techniques. These routine approaches however may be disappointing in the assessment of many conditions and occasionally fail to render a precise diagnosis or provide adequate prognostic information. Consequently there has been growing interest within the histopathological community in the state of the nucleus, DNA and proliferation markers. One of the most recent produces of this interst is the study of Nucleolar Organiser Regions (NORs) using a simple silver reduction technique (AgNOR method). Nucleolar organiser regions are an essential part of the machinery of the nucleolus (Howell, 1982; Derenzini et al., 1983). They can be seen as electron lucent areas at the ultrastructural level (fibrillar centres) which are the inter-phase equivalent of the condensed chromosomal NORs (Jordan & McGovern, 1981; Hernandez-Verdun, 1986). These structures can be seen at the light microscope level using a variety of techniques including the AgNOR method (Hsu et al., 1975; Ploton et al., 1986). They are involved in ribosome production and potentially qualitative or quantitative changes in interphase NORs may be visible in relation to proliferative activity or transformation and could aid diagnosis or prognostication. © Macmillan Press Ltd., 1992.