Invasive Mole (chorioadenoma destruens)
Invasive mole is a very rare condition in the UK. The use of routine ultrasound, the early evacuation of complete moles and effective hCG surveillance means that very few women have this diagnosis.
Invasive mole usually arises from a complete mole and is characterised by invasion of the myometrium, which can lead to perforation of the uterus. Microscopically invasive mole has a similarly benign histological appearance as complete mole but is characterised by the ability to invade in to the myometrium and the local structures if untreated.
The usual presentation is with hCG elevations following a previous molar pregnancy, other clinical features can include abnormal bleeding, abdominal pain or swelling.
Gestational Choriocarcinoma
Choriocarcinoma is clinically and histologically overtly malignant and presents the most common emergency medical problems in the management of trophoblast disease.
The diagnosis most frequently follows a CM when the patients are usually in a surveillance programme but can also arise in unsupervised patients after a non-molar abortion or a normal pregnancy.
The clinical presentation of choriocarcinoma can be from the disease locally in the uterus leading to bleeding, or from distant metastases that can cause a wide variety of symptoms with the lungs, central nervous system and liver the most frequent sites of distant disease.
Choriocarcinoma presenting with distant metastases can present some diagnostic challenges, however the combination of the reproductive/gynaecology history and elevated serum hCG usually makes the diagnosis apparent and so avoid a biopsy which can be hazardous from the risk of haemorrhage.
On the occasions that pathology is available the characteristic findings show the structure of the villous trophoblast but with sheets of syncytiotrophoblast or cytotrophoblast cells, haemorrhage, necrosis and intravascular growth is common.
In contrast to molar pregnancies the genetic profile of choriocarcinoma gives a range of gross abnormalities without any specific characteristic pattern.
Placental Site Trophoblastic Tumour (PSTT)
Placental site trophoblast tumours were first described in 1976 (Kurman 1976) and are the least common form of gestational trophoblast disease comprising less than 2% of all cases. PSTT most commonly follows a normal pregnancy but may occur after a non-molar abortion or a complete molar pregnancy and recently a case was reported following a partial mole.
In contrast to the other types of trophoblast disease which characteristically present fairly soon after the index pregnancy, in PSTT the average interval between the prior pregnancy and presentation is 3.4 years. The clinical presentation of PSTT can range from slow growing disease limited to the uterus to more rapidly growing metastatic disease that is similar in behaviour to choriocarcinoma.
The most frequent presentations are abnormal bleeding or amenorrhea. Usually the hCG levels, whilst elevated, are relatively low in PSTT relative to the volume of the disease compared to the other types of GTT.
PSTT is diploid and arises from the non-villous trophoblast and the pathology is characterised by intermediate trophoblastic cells with vacuolated cytoplasm, the expression of PLAP rather than hCG and the absence of cytotrophoblast and villi.