With the development of melanomas, it is possible that factors (perhaps cytokines including MIF, etc.)are systemically released by tumors (or the tumor microenvironment) which inhibit entry of these normal melanocyte precursors into the circulation, and that melanoma cells expressing MLANA and MIF (but not TYR or MITF) begin to enter the circulation. The gene discussed is TYR; the disease is neoplasm.