Nucleolar organiser regions in small cell carcinoma of the bronchus.

An argyrophil technique for the demonstration of nucleolar organiser regions has been applied to routinely processed paraffin sections of 15 specimens of small cell carcinoma and 15 biopsy specimens infiltrated by lymphocytes. To avoid tautological problems, the nature of the specimens was confirmed by means of immunohistochemical staining for neurone specific enolase and leucocyte common antigen. The specimens of small cell carcinoma were readily differentiated from those containing lymphocytes by the argyrophil method, the range of mean number of nucleolar organiser regions per nucleus being 4.2-7.3 for small cell carcinoma cells and 0.9-1.7 for lymphocytes. This method separates malignant epithelial cells from benign lymphocytic cells and has potential in both clinical and research investigation of respiratory tumours.