Increased allelic loss in toluidine blue-positive oral premalignant lesions

Objective. Recent studies have shown that a loss of chromosome regions (loss of heterozygosity [LOH]) containing known or presumptive tumor suppressor genes is predictive of the cancer risk of oral premalignant lesions. This preliminary study investigated whether the dye toluidine blue (TB) preferentially stains oral premalignant lesions with LOH. This stain has been used by clinicians to delineate dysplasia/carcinoma in the oral cavity. Study design. The study included 32 patients with oral lesions who underwent biopsy after the assessment of TB dye retention. A total of 39 biopsy specimens were examined (14 hyperplastic, 25 dysplastic). Fourteen of the biopsy specimens were TB-negative. The specimens were analyzed for LOH at 10 microsatellite loci on 3 chromosome arms (3p, 9p, and 17p), and the LOH results of TB-positive samples were compared with those that were negative for the tissue staining. Results. TB-positive samples had a higher frequency of loss than TB-negative cases for loci on 3p (P = .013) and 17p (P = .049). In addition, more TB-positive cases showed a loss of multiple arms (>2 arms, P = .015), a pattern that has been associated with markedly increased cancer risk. Conclusion. The study results suggest that TB staining may help identify oral premalignant lesions with increased LOH and increased cancer risk.