ZFX and tumor of parathyroid gland: In contrast, the striking specificity of the genetic alterations we observed in R786/787 supports the idea that mutant ZFX is a direct-acting oncogene in the context of parathyroid adenomas, and suggests that only this exceedingly limited range of ZFX mutations is able to provide a crucial gain of function, or introduce a new function, needed to confer a selective advantage on a parathyroid tumor progenitor cell.