Incidence of postmolar gestational trophoblastic disease in androgenetic moles and the morphological features associated with low risk postmolar gestational trophoblastic disease.

In the present study, we evaluated the incidence of postmolar gestational trophoblastic disease (GTD) in molar pregnancy. We also validated the macroscopic diagnosis based on the Japan Society of Obstetrics and Gynecology (JSOG) classification. A total of 297 samples of hydropic villi were classified according to DNA polymorphisms as androgenetic moles, dispermic triploids, or biparental diploids (hydropic abortion), clinically corresponding to complete hydatidiform mole (CHM), partial hydatidiform mole (PHM), and hydropic abortion, respectively. These samples were also classified morphologically based on the JSOG classification. A follow-up study was performed to investigate the incidence of postmolar GTD. A subset of 267 samples eligible for testing were analyzed and diagnosed as androgenetic moles (232 cases), dispermic triploids (20 cases), and biparental diploids (15 cases). Most of the macroscopically diagnosed CHM cases were genetically androgenetic in origin. The PHM cases consisted of 30 androgenetic moles and 12 dispermic triploids. We reviewed the outcomes of 200 patients (178 cases of androgenetic mole, 13 cases of dispermic triploids, and nine cases of biparental diploids). Twenty-eight cases (16%) of androgenetic moles developed postmolar GTD. None of the patients with dispermic triploids developed postmolar GTD. Among the 28 patients who developed postmolar GTD, the shortest diameter of the largest hydropic villi was significantly longer than that of patients not developing postmolar GTD. None of the patients with androgenetic moles who had hydropic villi <2 mm in their shortest diameter developed postmolar GTD. For the patients with dispermic triploids, the risk of postmolar GTD is extremely low. The risk of postmolar GTD is also low in patients with androgenetic moles with small hydropic villi. The JSOG classification based on the morphology of hydropic villi is reliable for the diagnosis of CHM, but inaccurate for the diagnosis of PHM or "microscopic" moles.