Complex sentence: Gigantomastia is extreme growth of the breasts (i.e.10 pounds or more per breast); formally, it is bilateral benign progressive breast enlargement to a degree that requires breast reduction surgery to remove more than 4 lb of tissue on each side.
Split into simpler sentences: Gigantomastia is extreme growth of the breasts (i.e.10 pounds per breast and more). Gigantomastia means bilateral benign progressive breast enlargement to a degree that requires breast reduction surgery to remove more than 4 lb of tissue on each side.