Placental-Site Trophoblastic Tumor, from the CureRays guide library.

Placental-site trophoblastic tumor is a rare cancer that grows from leftover placenta cells after a pregnancy — unlike most pregnancy-related tumors it resists chemotherapy, so surgery (usually hysterectomy) is the main cure.

What it is.

Placental-site trophoblastic tumor (PSTT) is a rare form of gestational trophoblastic disease — a group of tumors that grow from the cells that would normally form the placenta. It develops at the spot in the uterus where the placenta had been attached, and it can appear months or even years after any kind of pregnancy, including a normal delivery, miscarriage, or abortion. It tends to grow slowly and stay in the uterus longer than other trophoblastic tumors. Its most important feature is that, unlike the much more common choriocarcinoma, PSTT is relatively resistant to chemotherapy — so surgery to remove the uterus (hysterectomy) is usually the key to cure. It makes only modest amounts of the pregnancy hormone beta-hCG, so doctors cannot rely on that marker as heavily as they do for other trophoblastic tumors, and human placental lactogen (hPL) staining of the tissue helps confirm the diagnosis. A long gap since the last pregnancy is one of the features that signals higher risk.

How radiation treats it.

Radiation damages the DNA inside cancer cells so they can no longer divide and survive, while normal cells are better at repairing themselves. For placental-site trophoblastic tumor, surgery is the main cure and chemotherapy plays a supporting role, so radiation is used only in selected situations — for example to control a spot in the brain or to ease symptoms. When it is used, it is given as short, painless daily sessions and leaves no radioactivity in your body, so you remain safe to be around family and children.

The ways we can treat it.

Surgery. Hysterectomy is the primary, potentially curative treatment for disease confined to the uterus, and surgery is also used to remove isolated areas of spread.

Radiation (selective). Radiation is not a standard part of PSTT treatment, but it can be used to control specific sites of spread — such as the brain — or to relieve symptoms when surgery and chemotherapy are not enough.

Palliative radiation. Short, targeted courses of radiation can ease pain, bleeding, or pressure from areas of resistant or recurrent disease.

Questions we hear often.

Why is surgery, not chemotherapy, the main treatment? Unlike most pregnancy-related tumors, placental-site trophoblastic tumor does not respond well to chemotherapy. Removing the uterus (hysterectomy) is the most reliable way to cure disease that is still confined to the uterus, which is why it is the cornerstone of treatment.

Can this tumor appear a long time after a pregnancy? Yes. PSTT can develop months or even years after any pregnancy — including a normal delivery, miscarriage, or termination. A long gap since the last pregnancy is actually one of the signs that the tumor may be higher risk.

Why isn't my beta-hCG level as useful here? PSTT makes only small amounts of the pregnancy hormone beta-hCG, so it is a less reliable marker than it is for other trophoblastic tumors. Doctors rely more on imaging, surgery, and tissue findings (such as hPL staining) to diagnose and follow this tumor.

This guide is informational only. It is not medical advice — please confirm anything here with your care team.