Childs et al. found that a single cell of the pituitary gland in rodents can contain both ACTH and FSH, and explained this observation as “transdifferentiation.” One cell type may be transformed into another owing to the genetic and epigenetic factors at play during tumor progression, and are often accompanied by different morphological changes (Vidal et al., 2000). This evidence concerns the gene POMC and neoplasm.