Division of Radiooncology, Deutsches Krebsforschungszentrum, 69120 Heidelberg, Germany
Subsequent to immunohistological procedures, counterstaining of tissue sections with methyl green is a useful alternative to haematoxylin, carmine and other dyes for nuclear staining. Methyl green has seven methyl groups. The seventh methyl group is easily lost and the dye reverts to crystal violet. Thus, there is invariably a small quantity of crystal violet mixed with the methyl green. The commercial product Methyl green 'CERTISTAIN' for microscopical staining from the Merck group (Merck, BDH/Gurr and EM Diagnostic Systems) is a closely related dye, Ethyl green, in which the seventh methyl group is replaced by an ethyl group. There exist several formulations for methyl green staining; a useful procedure is described.