Placental Site Trophoblastic Tumor Arising from Antecedent Molar Pregnancy

Objective: Placental site trophoblastic tumor (PSTT) is a rare form of gestational trophoblastic disease. Little is known about its pathogenesis and natural history.

Methods: This report describes two cases that arose in patients with documented complete hydatidiform moles and summarizes the antecedent prenatal histories of PSTTs based on a detailed Medline literature analysis.

Cases: A 28-year-old, G(2)P(2) female had a live, 12-week gestation fetus and a coexisting molar pregnancy. Her hCG levels dropped promptly from 1.5 million to 23,273 IU/ml after termination, but rose shortly thereafter together with the onset of recurrent vaginal bleeding. Curettage revealed persistent mole. Persistently elevated hCG led to hysterectomy disclosing a fundal PSTT. The second case was that of a 48-year-old, G(2) woman who presented with symptoms of preeclampsia, hyperthyroidism, and elevated hCG. Curettage yielded a complete hydatidiform mole. Although the hCG level decreased for a short period, it soon increased despite treatment with methotrexate. A second curettage revealed a PSTT.

Discussion: A Medline literature analysis of PSTT, which consists almost entirely of individual cases and several small series, disclosed that PSTT is preceded in 61% of cases by normal term pregnancy, 12% molar pregnancy, 9% spontaneous abortion, 8% therapeutic abortion, and 3% with ectopic pregnancy, stillbirths or preterm delivery. No information is known in 7%. This report describes two additional cases of PSTT preceded by complete molar pregnancy.

Conclusions: PSTT is a well recognized, but uncommon form of gestational trophoblastic disease. Although little is known about its pathogenesis, it is preceded not uncommonly by an abnormal pregnancy, including a molar pregnancy.