Experimental Rationale for Treatment of High-Risk Human Melanoma with Zinc Chloride Fixative Paste

BACKGROUND: Fixed-tissue micrographic surgery (Mohs) of melanoma has been shown by retrospective analysis to improve 5-year survival. OBJECTIVES: To determine whether zinc chloride fixative paste acts as an immune adjuvant to increase host resistance to melanoma. METHODS: We performed a murine study using the poorly immunogenic B16 melanoma of C57Bl6J mice, and the more immunogenic K1735p melanoma of C3H/HeN mice. Tumors were treated with zinc chloride paste and excised 24 hours later (Group 1), or simply excised (Group 2). Mice were challenged 7 days later with injection of melanoma cells at a distant site, and tumor growth in this second site was followed. RESULTS: K1735p melanomas developed at the challenge site in 69% of mice treated with excision versus 32% of mice treated with zinc chloride fixation (P < 0.025). Development of B16 melanoma was not altered by zinc chloride fixation. CONCLUSION: Zinc chloride fixation of the more immunogenic K1735p melanoma increased resistance to subsequent tumor challenge, suggesting that zinc chloride fixative paste acts as an immune adjuvant.