Monoclonality of endocrine tumours: What does it mean?

It is believed and hoped that clonality assignment of tumours predicts long-term behaviour, narrows the search for the putative pathogenic event or events, identifies the extent of involvement of surrounding and distant tissues and assesses the completeness of surgical clearance. It should define optimal therapeutic strategies, such as gene therapy, and the most fruitful directions for research. Because the histological characteristics that are central to establishing prognosis in most neoplasms are of limited value in endocrine tumours, the benefits of interpretation of clonality are potentially even more valuable and far-reaching in these tissues. So, can clonality be accurately defined and, if it can, can the distinction between a polyclonal expansion of cells that are simply 'obeying orders' and the presumed progeny of a single anarchic mutant be usefully made? This review comes to the conclusion that the answer is 'probably not'.