Besides being associated with X-linked mental retardation with growth hormone deficiency (via its poly-Ala tract expansion mutations) [250], as well as with X-linked hypopituitarism (via its over- and under-dosage) [251] and SOX3 copy number variation-related 46, XX sex reversal 3 (SRXX3) [252], SOX3 overexpression was shown to play a crucial role in tumor progression [253,254,255,256,257], placing this transcription factors into the oncogene category. This evidence concerns the gene SOX3 and neoplasm.