A study of the mechanism of the toluidine blue dye test

Toluidine blue is commonly used by endoscopists as a screening test for squamous cell carcinoma. Little information is available on the mechanism of vital staining as it is not preserved by conventional fixation. By using a simple method to stabilize toluidine blue, the authors were able to study the action of the dye under the light and electron microscope. The findings are reported.