Histologic diagnosis of gestational trophoblastic diseases (GTD)

Masaharu Fukunaga, M.D. Department of Pathology, the Jikei University Daisan Hospital, Tokyo, Japan Hydatidiform moles With the increased use of ultrasound hydatidiform mole (HM) is being diagnosed at increasingly early stages of gestation. As villous edema is not fully developed, we cannot make a diagnosis of HM by macroscopic observation. Furthermore, microscopically the classic features of complete mole (CM) may be lacking and CM can be easily misdiagnosed as partial mole (PM) or hydropic abortion (HA). The incidence of cases of PM have been increasing lately, however, it may be partly due to underdiagnosis of early CM as PM. Many PMs have been still misdiagnosed as HA. In our previous study, significant interobserver and intraobserver variability in the diagnosis of molar pregnancy was observed even among placental pathologists (1). Since the risk of persistent disease is 10 to 15% in CMs and 1 to 2% in PMs, and no serious consequences are observed in the majority of patients with PM, practically, a correct diagnosis of early CM is most important. Following are histologic features of early CM; diffuse or focal hydropic change of villi, bulbous or polypoid villi, focal or circumference trophoblastic hyperplasia, cellular villous stroma, network of capillaries, karyorrhexis in villous stroma, prominent placental site intermediate trophoblasts, and absence of embryo. Criteria of PM are; two populations of villi, normal sized villi and edematous villi, irregular villous outlines, focal mild syncytiotrophoblastic hyperplasia, central cistern, trophoblastic inclusion, and the presence of an embryo or fetus. p57 immunostaining is useful for differential diagnosis between CM and PM (2, 3). Villous cytotrophoblasts and stromal cells are negative for p57 in CM.