Is monoclonality in pituitary adenomas synonymous with neoplasia?

Summary The objective of clonality analysis is to help differentiate hyperplasia from neoplasia. If the clonality of different pituitary subpopulations is skewed rather than uniform it is possible that a physiological trophic response could, by displacing trophically inert cells, give rise to a potentially evanescent monoclonal expansion in the absence of spontaneous somatic mutation. Such a clonal temtory model would allow for the presence of cellular subsets (a feature difficult to explain in terms of classical neoplasia) and account for a number of unusual characteristics of pituitary adenomas including monoclonality, cyclical activity, lack of oncogene involvement. spontaneous resolution and quantitative but not qualitative changes in secretory activity seen, for example, in Cushing's disease.