September 29, 2005
Unlike early cancer-causing lesions that arise in most parts of the body, those in the mouth are often visible and accessible for biopsy. But accessibility raises a critical question: How can dentists and doctors tell by sight which abnormalities to biopsy? Toluidine blue, a liquid dye composed of tolonium chloride, offers a potentially simple, inexpensive, and sensitive chair-side solution. Practitioners swab the blue dye onto a suspicious oral lesion and, based on its retention and resulting telltale change in blue tint, determine with greater reliability whether to proceed to biopsy. As straightforward as the swab-and-wait process is, researchers have reported a major limitation: While toluidine blue staining detects most cancerous lesions, it frequently misses precancerous lesions of low or moderate grade.
But this limitation may in fact provide a diagnostic advantage. Two recent studies found an association between toluidine blue retention in early oral lesions that contain cells with distinct, cancer-predisposing chromosomal abnormalities, an indication that the dye may detect the low-grade lesions that are among the most likely to progress. Now, NIDCR grantees report new data in the September 1 issue of the journal Cancer Research that support this idea in people. The grantees monitored 100 patients with oral premaligant lesions for 44 months, allowing them to evaluate over time the possible association of toluidine blue staining and three factors: clinical pathology, several well characterized chromosomal aberrations, and outcome. They found toluidine blue detected 16 of 17 cases of high-grade dysplasia (early alterations in cell structure) in the study, and it preferentially stained the oral premalignant lesions with minimal or no dysplasia that had high-risk clinical and molecular attributes. The authors concluded that the study "points to a need to re-assess toluidine blue stain not just with its association with histology, but also with molecular risk predictors and with outcome."