CDKN2B and dysplastic nevus: Histopathological examination revealed that the development process of melanoma in cdkn2b-/-/tp53-/- frogs paralleled that in tp53-/- frogs 31, characterized by four stages: benign nevi, dysplastic nevi, non-invasive melanoma, and invasive melanoma (Figure 2B-D and Figure 3A), mirroring the progression of human cutaneous melanoma 40.