Most GTN cases are clinically diagnosed, using -hCG evidence of persistent trophoblastic tissue. Criteria for the Diagnosis of Gestational Trophoblastic Neoplasia: Plateau of beta-hCG lasts for four measurements over a period of 3 weeks or longer (days 1, 7, 14, and 21). Rise of beta-hCG of 3 weekly consecutive measurements or longer, over a period of 2 weeks or more (days 1, 7, and 14). beta-hCG remains elevated for 6 months or more. Histologic diagnosis of choriocarcinoma. Ref: Hoffman B.L., Schorge J.O., Schaffer J.I., Halvorson L.M., Bradshaw K.D., Cunningham F.G., Calver L.E. (2012). Chapter 37. Gestational Trophoblastic Disease. In B.L. Hoffman, J.O. Schorge, J.I. Schaffer, L.M. Halvorson, K.D. Bradshaw, F.G. Cunningham, L.E. Calver (Eds), Williams Gynecology, 2e.