Diagnosis:
Partial Hydatidiform Mole
• Gestational trophoblastic neoplasia is a heterogeneous group of diseases that classically include partial and complete hydatidiform moles, invasive moles, placental site trophoblastic tumor, and choriocarcinoma. Epithelioid trophoblastic tumor has been added to this family more recently.
• In the normal placenta, three types of trophoblasts have been identified: cytotrophoblasts, which are responsible for proliferation; syncytiotrophoblasts, which produce placental hormones; and intermediate trophoblasts, which have overlapping features between cytotrophoblasts and syncytiotrophoblasts.
• All trophoblastic cells are positive for human chorionic gonadotropin (HCG) and human placental lactogen to varying degrees. Human placental lactogen tends to be more strongly positive. Inhibin is expressed by syncytiotrophoblasts (useful in choriocarcinoma) and intermediate trophoblasts (useful in placental site trophoblastic tumors). Melanoma cell adhesion molecule is a specific and sensitive marker for intermediate trophoblasts in normal placentas, implantation sites, and gestational trophoblastic neoplasia. P57 can be used to differentiate partial hydatidiform moles (in which it is positive) from complete hydatidiform moles (in which it is negative).
• Patients with partial hydatidiform mole are less likely to have symptoms than patients with complete hydatidiform moles. Patients classically present with a missed abortion. There is some variation in the gross appearance of these lesions because the placental tissue is less bulky. Fewer vesicles are present compared with complete hydatidiform moles. An identifiable fetus or fetal parts may be present.
• Histologically, one observes a mixture of normal villi and hydropic villi. The hydropic villi demonstrate variable levels of swelling with central cisterns present to a lesser degree than in a complete mole. The outline is often irregularly scalloped, and trophoblastic inclusions are seen. Fetal parts may be seen. Blood vessels containing fetal normoblasts also may be present.
