A gestational trophoblastic tumour (GTT) is a rare condition that arises in the placenta. Cancer begins when normal cells begin to change and grow uncontrollably, forming a mass called a tumour. A tumour can be benign (noncancerous) or malignant (cancerous, meaning it can spread to other parts of the body.) A GTT is most commonly the result of an abnormal pregnancy due to an abnormal combination of a sperm and an egg. In other cases, a GTT is a cancerous growth that begins from a normal placenta. The placenta is the organ that develops during pregnancy and connects the fetus (unborn baby) to the uterus, also called the womb. For further information, please click on the links below.