Gestational trophoblastic disease (GTD) comprises a wide spectrum of neoplastic disorders that arise from placental trophoblastic tissue after abnormal fertilization (Fig. 34-1). The spectrum includes benign disease (complete and partial hydatidiform moles) and malignant gestational trophoblastic neoplasia (GTN), which includes choriocarcinoma, placental site trophoblastic tumor (PSTT), and epithelioid trophoblastic tumor (ETT) (1). Invasive moles may also occur and are best categorized as malignant, since they can metastasize. Gestational trophoblastic neoplasia is also described as gestational trophoblastic tumor (GTT) and is further designated as nonmetastatic or metastatic (2).
Gross specimen of two complete molar pregnancies. Note the absence of fetal tissue, which is replaced by abundant trophoblastic tissue.
The hydatidiform mole is the most common type of GTD. It is essentially a benign condition with variable potential for malignant transformation. Most molar pregnancies resolve spontaneously after uterine evacuation, with no further events or adverse outcomes. At any time during or after gestation, approximately 20% undergo malignant transformation to invasive nonmetastatic or metastatic GTN and require further treatment (3). Nearly two-thirds of these lesions develop into persistent nonmetastatic GTN; the remaining one-third develop distant metastases (2,4).
These tumors were first described around 400 B.C. by Hippocrates and subsequently termed “dropsy” of the uterus. During the 1950s, the 5-year survival of patients with choriocarcinoma was less than 5%. The treatment of these tumors has been revolutionized with effective chemotherapy, leading to a cure rate approaching 100% and fertility preservation in most patients (1,5,6). Successful outcomes rely on individualized management based on careful staging and treatment planning by a multidisciplinary team.
The prevalence of GTD depends on geography, maternal age, previous GTD history, socioeconomic factors, dietary factors, and blood grouping. True estimates of the incidence of molar pregnancy are difficult to obtain because of the vast variation in presentation and management of normal and abnormal pregnancies around the world. In North America and in Europe, GTD develops in approximately 1 in 100 to 2,000 pregnancies (1,7,8). A higher rate of 1.5 to 6 per 1,000 pregnancies has been reported in South America. Early observations comparing East and Southeast Asian countries with the United States suggest a 5- to 15-fold higher incidence, as high as 1 in 120 pregnancies in East Asia (1,8,9). Native Alaskans have an incidence three- to fourfold that of white women. Native Americans had a higher incidence than other ethnic groups in New Mexico (10). Not all data confirm the importance of ethnic background. Recent analyses suggest that the incidence in Southeast Asia is similar to that in Europe, which may reflect modifications in diet, improved diagnosis, and improved capture ...