Certain neoplastic lesions of mucous membranes have been shown to stain after topical application of toluidine blue dye. Richart1 first reported the use of toluidine blue dye as a vital stain for dysplasia and carcinoma of the uterine cervix. Since then Niebel and Chomet,2 Shedd et al,3,4 Iwano et al,5 and Strong et al6 have demonstrated its diagnostic value in lesions of the mouth and pharynx, while Collins et al7 studied staining of vulvar lesions. Squamous carcinomas, both invasive and in situ, and certain dysplastic lesions of these mucous membranes were stained a blue color by the dye. Staining also occurred in areas of ulceration. Subepidermal extensions of squamous cell carcinomas did not stain but satellite lesions in the mucosa were detected by stain.
Discovery of early primary or recurrent skin cancer is dependent on the arousal of clinical suspicion which leads to biopsy.