Gestational Trophoblastic Tumors and Related Tumor-Like Lesions

Abstract

Gestational trophoblastic disease (GTD) encompasses a heterogeneous group of lesions with specific clinical features, morphological characteristics, and pathogenesis. The World Health Organization classification of GTD includes complete and partial hydatidiform mole, invasive mole, choriocarcinoma, placental site trophoblastic tumor (PSTT), epithelioid trophoblastic tumor, exaggerated placental site, and placental site nodule (Table 20.1 ) [145]. Some of these lesions are true neoplasms, whereas others represent abnormally formed placentas with a predisposition for neoplastic transformation of the trophoblast. Two benign entities, the exaggerated placental site and the placental site nodule, are included because they are trophoblastic lesions that must be distinguished from other entities with malignant potential. The literature on GTD is extensive and at times confusing because of inconsistencies in classification and terminology. In fact, the necessity of a morphologic classification has been questioned, because current management is largely medical and in the case of trophoblastic disease following a mole, treatment is often conducted in the absence of a histological diagnosis. Thus, all trophoblastic lesions are frequently combined under the rubric of GTD without applying specific pathological terms. However, recent studies demonstrate profound differences in the etiology, morphology, and clinical behavior of various forms of the disease. These studies underscore the importance of a uniform histological classification to facilitate standardized reporting of data and to ensure appropriate clinical management. Nonetheless, the term GTD has clinical utility, as the principles of human chorionic gonadotropin (hCG) monitoring in follow-up and the chemotherapy of metastatic or persistent disease are similar for all these entities.