DEMONSTRATION OF MONOCLONAL ORIGIN OF HUMAN PAROTID-GLAND PLEOMORPHICADENOMA

BACKGROUND. Parotid gland pleomorphic adenoma is histologically compri sed of epithelial and mesenchymal elements. It remains to be establish ed whether this neoplasm arises from epithelial and mesenchymal elemen ts, or solely from the epithelial element. METHODS. In an attempt to r esolve this issue, we have conducted clonal analysis on five pleomorph ic adenomas. The method for clonal analysis was based on the trinucleo tide repeat polymorphism of the x-chromosome-linked androgen receptor gene and on random inactivation of this gene by methylation. The epith elial and mesenchymal elements were obtained separately from the paraf fin sections of the pleomorphic adenomas using a microdissection techn ique and then subjected to clonal analysis. RESULTS. Clonal analysis r evealed that both epithelial and mesenchymal elements were monoclonal. In addition, the same allele of the androgen receptor gene was inacti vated in both elements in every case. CONCLUSIONS. It is unlikely that the epithelial and mesenchymal elements of different origin happen to inactivate the same allele of the androgen receptor gene in all five tumors. Rather, it is more reasonable to consider that these two eleme nts have a common single cell origin. (C) 1996 American Cancer Society .