Recently, Melillo et al [22], while analyzing the transforming activity of RET mutations in PC CI3 follicular cells, in case of a family with affected siblings showing a collision tumor, postulated that RET point mutants behave as conditional oncogenes, able to predispose to PTC only under specific circumstances, such as, high level expression of the mutated allele in follicular cells. This evidence concerns the gene RET and neoplasm.