Complete molar pregnancies are generally diploid and all chromosomes are of paternal origin.
Partial molar pregnancies are triploid and the extra set of chromosomes is paternal.
Complete moles are diagnosed earlier in pregnancy and less frequently present with the classic signs and symptoms.
Single-agent chemotherapy achieves a high remission rate in nonmetastatic and low-risk metastatic gestational trophoblastic neoplasia.
After achieving remission with chemotherapy, patients with gestational trophoblastic neoplasia can anticipate normal reproduction in the future.
Gestational trophoblastic disease (GTD) is the term used to describe the heterogeneous group of interrelated lesions that arise from abnormal proliferation of placental trophoblasts. GTD lesions are histologically distinct and can be benign or malignant. Benign lesions consist of hydatidiform moles, complete and partial, whereas malignant lesions consist of invasive mole, placental-site trophoblastic tumor (PSTT), and choriocarcinoma. This subset of malignant lesions that have varying propensities for local invasion and metastasis is referred to as gestational trophoblastic neoplasia (GTN). GTNs are among the rare human tumors that can be cured even in the presence of widespread dissemination (1,2). Although GTNs commonly follow a molar pregnancy, they can occur after any gestational event, including induced or spontaneous abortion, ectopic pregnancy, or term pregnancy.
Epidemiology Estimates of the incidence of molar pregnancy vary dramatically in different regions of the world. For example, the incidence of molar pregnancy in Japan (2:1,000 pregnancies) is reported to be about threefold higher than the incidence in Europe or North America (about 0.6 to 1.1 per 1,000 pregnancies) (3). In Taiwan, 1 in 125 pregnancies are molar, while in the
Table 39.1 Features of Complete and Partial Hydatidiform Moles
United States the incidence is 1 in 1,500 live births. The incidences of complete and partial hydatidiform mole in Ireland were investigated by reviewing all products of conception from first-and second-trimester abortions (4). Based on a thorough pathologic review, the incidence of complete and partial hydatidiform mole was 1:1,945 and 1:695 pregnancies, respectively.
While variations in the worldwide incidence of molar pregnancy may result in part from reporting population-based versus hospital-based data, a number of studies suggest that the high incidence in some populations can be attributed to socioeconomic and nutritional factors. The decreasing incidence of molar pregnancy in South Korea is attributed to a more Western diet and improved standard of living (5). Case-control studies from Italy and the United States show that the rate of complete mole increases with decreasing consumption of dietary carotene (vitamin A precursor) and animal fat (6,7). Maternal age and reproductive history inﬂuence the rate of molar pregnancy. Women older than 40 years have a 5-to 10-fold greater risk of having a complete mole, while one in three pregnancies in women older than 50 years results in a molar gestation (8,9). These findings suggest that ova from older women may be more susceptible to abnormal fertilization, resulting in a complete hydatidiform mole.
Limited information is available concerning risk factors for partial molar pregnancy. The epidemiologic characteristics of complete and partial mole appear to differ significantly (8–11). The risk for partial mole is associated with the use of oral contraceptives and a history of irregular menstruation, but not with dietary factors (10). Nor does there appear to be an association between maternal age and the risk for partial mole.
Pathology and Hydatidiform moles may be categorized as either complete or partial moles on the basis of gross Cytogenetics morphology, histopathology, and karyotype (Table 39.1).