Effect of melanin bleach on Feulgen-DNA microdensitometry in pigmented lesions.

OBJECTIVE: To investigate the effect of melanin bleach on Feulgen-DNA microdensitometry in pigmented melanocytic lesions. STUDY DESIGN: Twenty banal compound nevi with various grades of pigmentation were bleached by 0.5% and 1% KMnO4 for 0 to 20 minutes and by 10% H2O2 for 24 hours prior to Feulgen staining. DNA microdensitometry was performed by video image analysis to measure the integrated optical density (IOD) in nuclei from nevomelanocytes, lymphocytes and spinous keratinocytes. The DNA index of nevomelanocytes was calculated using spinous keratinocytes as the diploid controls. RESULTS: There were significant decreases in IOD (P < .05) in the nuclei of nevomelanocytes, lymphocytes and spinous keratinocytes after treatment with 1% KMnO4 for 5 and 10 minutes, but no significant changes were detected after treatment with 0.5% KMnO4 for 5 and 10 minutes. Severe tissue damage was observed in the Feulgen-stained slides treated with 1% KMnO4 for 15 and 20 minutes and with 10% H2O2 for 24 hours. There was no significant change in DNA index in any bleached sets measured. CONCLUSION: KMnO4 can affect Feulgen-DNA content if used in high concentrations or for long periods of incubation. The DNA index, which is derived from internal controls, is not affected by the bleach procedure.