Placental site trophoblastic tumours (PSTTs) happen after pregnancy. They are extremely rare and are slow growing and usually curable.
What a placental site trophoblastic tumour is
Placental site trophoblastic tumours are very rare. Fewer than 5 women are diagnosed in the UK with PSTT each year.
They are part of a group of conditions called gestational trophoblastic disease (GTD for short). Less than 1 in 100 (1%) GTDs are placental site trophoblastic tumours.
It is important to realise that PSTT is not the same as womb cancer. In womb cancer the cancer develops from the cells of the womb lining (the endometrium). In PSTT the tumour develops from the cells that grow to form the placenta. The cells are called trophoblast cells.
Placental site trophoblastic tumours (PSTTs) happen after pregnancy. They can happen after any type of pregnancy, including molar pregnancy, miscarriage, abortion, or a full term normal pregnancy. They can occur several months, or even years, afterwards.
These tumours develop in the area where the placenta joined the lining of the womb (uterus). They can grow into the muscle layer of the womb. They are slow growing and are usually curable.
In some women PSTT can spread beyond the womb. It is most likely to spread to the lungs or to the body structures surrounding the womb.
Symptoms of PSTT
The main symptom of PSTTs is irregular bleeding from the vagina, which in some women follows a loss of periods (amenorrhoea).
If you have vaginal bleeding or your periods have stopped your doctor will refer you for tests. You might have the following tests.
Women with PSTT tend to have raised levels of a hormone called human chorionic gonadotrophin (hCG) in their blood. This hormone is produced by the PSTT cells.
The ultrasound scan might show abnormal areas in the lining of the womb. A special type of scan called a Doppler ultrasound uses colour to show up body structures. The Doppler scan can show that there are more blood vessels than usual in the area of the tumour.
Surgery to sample the womb lining
You have the operation under general anaesthetic in hospital. Once you are asleep, the surgeon opens up (dilates) the entrance to the womb (cervix) and takes a sample of any abnormal areas. The doctor uses a small instrument called a curette to scrape the lining of the womb. They send the tissue they have removed to the laboratory. Under the microscope a pathologist can tell that the cells are a PSTT.
Treatment for placental site trophoblastic tumour
If the tumour is only in the womb the main treatment is surgery. Most women have removal of the womb (a hysterectomy). If your doctor can remove the whole tumour in this way it should cure the condition.
In younger women who want to have more children, sometimes it is possible to surgically remove just the tumour tissue. But the tumour tissue might come back. So these women need to have regular blood tests to check levels of the hormones, hPL and hCG.
If the levels of the hormones start to rise, or if the woman develops any other symptoms that the tumour has come back, they will need to have a hysterectomy.
If the PSTT has spread to another part of your body, such as the area around the womb or the lungs, you will need chemotherapy after surgery. The treatment usually involves a combination of chemotherapy drugs. The drugs used may include:
- actinomycin D
The treatment is given until the hCG level is normal and then for a further 8 weeks.
Follow up after treatment
After treatment your specialist will monitor you closely. You might need ultrasound scans, MRI scans, CT scans and urine tests to check how well the treatment has worked and to monitor your progress.