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To select the optimal immunohistochemical staining method for pigmented melanoma
Juan Lin1,2, Zhijie You1,2, Xin Chen3,4
1Shengli Clinical Medical College, Fujian Medical University, Fuzhou, 350001, Fujian Province, China.
Abstract:
Melanin granules may be difficult to distinguish from the brown reaction product of 3,3'-diaminobenzidine (DAB) in immunostaining. To identify a reliable immunostaining protocol for pigmented melanoma that preserves tissue integrity while enabling clear observation of antigen-antibody binding. Ki67 and the human melanoma black 45 (HMB45) immunostaining was performed on 30 pigmented melanoma specimens using three methods: (1) Unbleached control, (2) Bleached with 5% H₂O₂, (3) Alkaline Phosphatase-3-Amino-9-Ethylcarbazole (AP-AEC). Compared with the unbleached control, the coincidence rates of Ki67 and HMB45 expression in bleached with 5% H2O2 group were 90.9% and 86.4%, respectively, and the one in AP-AEC group were 81.8% and 90.9%, respectively. No significant differences (all p > 0.05) in Ki67 expression and HMB45 expression parameters (percentage, staining intensity and H-score) between bleached group vs. unbleached control and AP-AEC group vs. control across all comparative measured parameters. A 25% (4/16) tissue damage rate occurred in heavily pigmented specimens subjected to the bleaching group, and non-specific staining were observed in AP-AEC processed samples. For lightly pigmented melanoma, bleached with 5% H2O2 method optimally balanced tissue preservation and staining reliability. Non-specific immunostaining was observed in the AP-AEC group. For heavily pigmented melanoma, AP-AEC method minimized tissue damage despite minor non-specificity.
Insights
For pigmented melanoma, bleaching with hydrogen peroxide (H₂O₂) offers reliable Ki67 and HMB45 immunostaining in lightly pigmented tissues. The Alkaline Phosphatase-3-Amino-9-Ethylcarbazole (AP-AEC) method is better for heavily pigmented melanomas, minimizing damage.
Area of Science:
- Oncology
- Histopathology
- Immunohistochemistry
Background:
- Melanin granules in pigmented melanoma can obscure 3,3'-diaminobenzidine (DAB) staining.
- Reliable immunostaining protocols are needed to preserve tissue integrity and visualize antigen-antibody binding in melanoma.
Purpose of the Study:
- To evaluate and compare different immunostaining protocols for pigmented melanoma.
- To identify optimal methods for Ki67 and human melanoma black 45 (HMB45) detection in pigmented melanoma specimens.
Main Methods:
- Investigated three immunostaining methods: Unbleached control, 5% hydrogen peroxide (H₂O₂) bleaching, and Alkaline Phosphatase-3-Amino-9-Ethylcarbazole (AP-AEC).
- Performed Ki67 and HMB45 immunostaining on 30 pigmented melanoma specimens.
- Assessed staining coincidence rates, tissue integrity, and non-specific staining.
Main Results:
- Bleaching with 5% H₂O₂ showed high coincidence rates (90.9% for Ki67, 86.4% for HMB45) in lightly pigmented melanoma, balancing preservation and reliability.
- AP-AEC method demonstrated high coincidence rates (81.8% for Ki67, 90.9% for HMB45) and minimized tissue damage in heavily pigmented melanoma, despite minor non-specificity.
- No significant differences in staining parameters were observed between bleached/AP-AEC groups and the control.
Conclusions:
- For lightly pigmented melanoma, 5% H₂O₂ bleaching is optimal for reliable Ki67 and HMB45 immunostaining.
- For heavily pigmented melanoma, AP-AEC method is preferable to minimize tissue damage, with acceptable non-specificity.
- Protocol selection depends on melanoma pigmentation levels for accurate immunohistochemical analysis.
