Application of the Method of Melanin Bleaching After Immunohistochemical Staining of Melanin-containing Tissues

OBJECTIVE: The purpose of this research was to investigate the method of melanin bleaching in immunohistochemical staining of melanin-containing tissues. MATERIALS AND METHODS: Forty melanin-containing tissue samples were selected, including 30 with malignant melanoma and 10 with blue naevi. The samples were divided into the following 3 groups: the prestaining bleaching group, nonbleaching group, and poststaining bleaching group. Each group was subjected to HMB45 and MelanA immunohistochemical staining. The detection system used was Roche ventana ultraview universal alkaline phosphatase red kit. RESULTS: In the prestaining bleaching group, melanin pigment was mostly removed. However, antigen expression was also affected, which resulted in significantly weaker positive staining and even represented false-negative expression. In the nonbleaching group, positive staining resulted in a red color that could easily be distinguished from the brown granules of melanin pigment. However, some melanin granules covered the tissue, impacting our observation of tissue structure. In the poststaining bleaching group, the results of positive staining were comparable to those in the nonbleaching group. The melanin pigment in these sections was almost completely removed, resulting in clearer staining and easier observation of tissue and cell structure. CONCLUSION: The method of melanin bleaching after immunohistochemical staining of melanin-containing tissue can almost completely bleach the melanin pigment and do not impact the expression of antigen. In our work, poststaining bleaching allowed for clearer immunohistochemical staining results and more obvious observation of tissue structure. This method also has the advantages of requiring simple reagents, utilizing simple operation procedures, and producing practical staining results, which makes it worthy of promotion!