Mechanisms of growth in hydatidiform moles.

Nuclear morphology and DNA synthesis were analyzed to determine the mechanism through which hydatidiform moles proliferate. Hydatidiform moles are characterized by a great variation in nuclear morphology and size. There are cells with small nuclei of variable size that have chromocenters and Barr bodies which do not undergo DNA synthesis or mitosis, as well as cells in the diploid range that have evenly stained nuclei that display numerous mitoses and a high proportion of interphase nuclei in the process of DNA synthesis. Nuclei in the medium range show classical endomitotic stages. Endomitotic nuclei in endometaphase do not label with tritiated thymidine; endoanaphase nuclei may have one or a few chromosomes labeled, and endotelophase nuclei are heavily labeled. Nuclei that are evenly stained and are in the medium- to giant-size range label differently, depending upon their size. Many of the medium-sized nuclei are labeled, indicating DNA synthesis; the large nuclei are rarely labeled, and the giant nuclei are never labeled. The growth of a hydatidiform mole appears to be the result of normal mitosis and cytokinesis, as well as polyploidization and accompanying cell enlargement achieved through endomitosis and endoreduplication.