496 Obstetrics and Gynecology Board Review •••
❍ What percentage of patients have metastatic disease when GTD is diagnosed?
45%.
❍ What percentage of patients treated for nonmetastatic GTD with negative chest X-ray have pulmonary
metastasis noted on chest CT?
29% to 41%.
❍ What is the most common site of metastasis for GTD?
Lungs.
❍ What is the preferred single-agent chemotherapy of choice?
Methotrexate.
❍ Why is methotrexate the preferred method?
Less toxicity and greater ease of administration make methotrexate a more attractive agent. Dactinomycin is
generally reserved for secondline therapy, although both single-agent therapies yield similar response rates.
❍ What is an adequate response to chemotherapy?
A fall in the hCG level by 1 log after a course of chemotherapy.
❍ Describe the characteristics of gestational choriocarcinoma.
Gestational choriocarcinoma contains both cytotrophoblast and syncytiotrophoblast elements. Chorionic villi
are absent, and if present represent an invasive molar pregnancy. Gestational choriocarcinoma readily invades the
maternal venous system, producing metastasis by hematogenous dissemination. Metastases tend to outgrow their
blood supply, resulting in central necrosis and often massive hemorrhage.
❍ Describe the characteristics of PSTTs.
PSTTs are composed of a predominance of intermediate cytotrophoblast cells arising at the site of placental
implantation. Because there is only a small proportion of syncytiotrophoblast cells, little beta-hCG is produced.
In some patients, human placental lactogen (hPL) is a more reliable marker. These tumors are locally invasive,
although a small percentage of patients will develop extrauterine metastasis.
❍ What is the treatment of PSTT?
These are not sensitive to chemotherapy; therefore, surgery (hysterectomy) becomes the main treatment.
❍ What is the highest risk factor for having a choriocarcinoma?
A hydatidiform mole in the previous pregnancy confers the greatest risk of the development of a subsequent
gestational choriocarcinoma.