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.