Demonstration of argyrophil granules in small cell carcinoma of the lung.

The Grimelius silver nitrate stain has enabled us to demonstrate the presence of tumor cells with argyrophil granules (argyrophil cells) in small cell carcinoma of the lung. Of the 22 tumors, 11 showed varying numbers of argyrophil cells. The occurrence of the cells differed in frequency among the subtypes of small cell carcinoma. The fusiform cell type showed the cells more frequently than the other types. Both tumors with numerous argyrophil cells belonged to the fusiform cell type. The number of positive cells seen under the light microscope did not correlate with the number of cells containing neurosecretory granules under the electron microscope, nor with the amount of either ACTH or serotonin in the tumor extracts. The demonstration of these cells in a pulmonary carcinoma may be of help in making correct histological diagnosis.