FIGURE 1: The route of inoculation determines tumour penetrance in transplantable models of cutaneous melanoma. Intradermal and subcutaneous inoculations of B16 melanoma cells (purple) result in complete tumour penetrance. By contrast, application of B16 melanoma cells onto the outermost layer of skin (epicutaneous inoculation) results in reduced tumour penetrance. Of note, the majority of non-developer mice show signs of long-term persistence of melanoma cells (melanoma-immune equilibrium).