In contrast, tissues and organs can also get larger by another mechanism, hyperplasia, in which the cells remain approximately the same size but increase in number. Although hypertrophy and hyperplasia are two distinct processes, they frequently occur together. The hormonally-induced proliferation and enlargement of the cells of the uterus during pregnancy is an example of this combination under normal conditions. In some tumors, enlargement can occur by an increase in the number of cells together with the occurrence of some abnormally large cells.