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

OBJECTIVE: To investigate the effect of melanin bleach oil Feulgen-DNA micr odensitometry in pigmented melanocytic lesions. STUDY DESIGN: Twenty banal compound nevi with various grades of pigmentatio n were bleached by 0.5% and 1% KMnO4 for 0 to 20 minutes and by 10% H2O2 fo r 24 hours prior to Feulgen staining. DNA microdensitometry was performed b y video image analysis to measure the integrated optical density (IOD) in n uclei 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 necvomelanocytes, lymphocytes and spinous keratinocytes after treatment wit h 1% KMnO4 for 5 and 10 minutes, but no significant changes were detected a fter treatment with 0.5% KMnO4 for 5 and 10 minutes. Severe tissue damage w as 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 ill DNA index in any bleached sets measured. CONCLUSION: KMnO4 can affect Feulgen-DNA content if used in high concentrat ions or for long periods of incubation. The DNA index, which is derived fro m internal controls, is not affected by the bleach procedure.