Differential staining of mitoses in tissue sections and cultured cells by a modified methenamine-silver method

By a modification of Gomori's methenamine-silver method applied to formalin-fixed tissue and cultured cells, a rapid and reproducible technique was developed, whereby mitotic figures could be stained with high contrast as compared with nonmitotic nuclei. In fact, in cultured cells counterstaining was necessary to identify the nuclei of nondividing cells. The method was applied to a variety of tumors of epithelial or mesenchymal origin. Apart from mitoses, inflammatory cells and stroma were also stained, but the discrimination of mitotic cells was nevertheless much facilitated in most tumors, particularly in solid epithelial ones with scanty stroma. The staining probably involves an association of chromosomal proteins with silver ions, the formalin fixation making it possible to omit the usual initial oxidation step. The mitotic rate is known to be a powerful prognostic factor for malignancy and the staining technique should make it easier to identify mitoses, hence facilitating counting, e.g., with computer-assisted image analysis.