Toluidine blue is a metachromatic dye that binds to DNA in vital tissues. It has been used for decades and was originally used for cervical screenings. It is not cancer specific, but it has been reported to stain cells with increased amounts of DNA and possibly altered DNA in premalignant and malignant epithelial lesions. The product is usually applied topically followed by rinsing with water then blotting with 1% acetic acid. Toluidine blue can be obtained from most compounding pharmacies.