Placenta Site Trophoblastic Tumor (PSTT)

dr yousefi Gynecologist oncologist of Medical Sciences of Mashhad University

Placental site trophoblastic tumor is a rare neoplasm that arises from intermediate trophoblasts and shows diversity of biological behaviors, resulting in the absence of consistency in treatment modalities

the term placental site trophoblastic tumor was introduced by Scully and Young in 1981 and subsequently accepted by the World Health Organization (1994)

PSTT is the rarest form of GTN, but deserves separate consideration, as it behaves in a distinct fashion.

This represents a neoplastic proliferation of intermediate trophoblasts that invade the myometrium at the placental site after pregnancy

Unlike other forms of malignant GTN, PSTT is often more slow growing, tends to spread locally through the uterus and

can involve lymph nodes (a very rare finding for choriocarcinoma) before metastasizing elsewhere

PSTT also tend to be relatively poorly vascularized tumours and Due to the lack of syncytiotrophoblastic tissue, serum hCG levels are often only modestly elevated

Hpl and prolactin

Free beta HCG are useful

ultra sonography of PSTT may also appear as a heterogeneous, hyperechoic mass with multiple cystic spaces within the myometrium of an enlarged uterus.

These features alone do not allow distinction from other forms of GTN,

though on Doppler both hypervascular and hypovascular forms of the disease have been described with or without cystic masses, but none of these features are diagnostic of PSTT.

MRI does not have a role in routine assessment of persistent disease following a CHM or PHM, and is only indicated in difficult cases such as in relapsed patients, suspected PSTT, or very advanced disease.

The MRI findings in GTN can be relatively non-specific, and it may be difficult to distinguish GTN from an incomplete miscarriage or an ectopic pregnancy

The behavior of PSTT has not been well predicted by the traditional prognostic scoring system of Bagshawe for gestational trophoblastic disease and needs to be considered separately

Several systems have been used to classify the severity of GTN, including the

Bagshawe scoring system ,WHO score, and Charring Cross Hospital prognostic scoring

system . These all use factors that have long been

recognized as predictive of poor outcome.

More recently a new International Federation of Gynecologists and Obstetricians (FIGO) scoring system has been developed and most centers use this to enable better comparison of patient response and outcome

Factors significantly associated with poor survival were

high stage, long pregnancy interval, high mitotic rate, and high maximum serum hCG levels.

A previous term pregnancy was associated with poor prognoses

high mitotic rate, coagulative necrosis, clear cytoplasm, and high serum hCG were all significantly associated with higher stage

tumors .

depth of myometrial invasion of one third ,

mitotic rate of 6 per 10 HPF, and serum hCG levels of 1000 mIU/ml.

Age greater than 35 years, interval from antecedent pregnancy

of >2 years, and prior term pregnancy

were significant prognostic factors in the current series

Recurrent disease always manifests itself with a rising hCG and this should prompt repeat whole-body imaging including a Doppler ultrasound of the pelvis.

The standard treatment for

PSTT is hysterectomy

Some patients that have been treated with only a dilatation and curettage or other uterine sparing surgery

conservative surgical treatment may have a role in patients with

stage I tumors who wish to conserve fertility,

as long as their tumors do not have unfavorable prognostic features.

This usually consists of local excision by hysterotomy

PSTTs usually are locally aggressive, with invasion into the myometrium. They are typically resistant to traditional

chemotherapeutic agents .

single agent chemotherapy is not effective and

Multiagent chemotherapy has had better success .

surgical resection of chemoresistant metastatic PSTT may be a reasonable option.

For cases refractory to chemotherapy, radiation, and surgery ,

few treatment options exist. Several commercially available agents of this

class

EMA/EP is advocated for salvage treatment in patients previously

treated with EMA/CO .

Chemotherapy regimens used for unresectable and progressive PSTT have included EMA/EP

,bleomycin–etoposide–cisplatin, etoposiode–ifosfamide–cisplatin ,

regimen of cisplatin, etoposide,

On going to such rapid progression after receiving EMACO,

resistance to this particular regimen was presumed and an alternative regimen

of taxol, etoposide, and cisplatin was chosen used

Newer drugs that target growth factor receptors might provide a novel therapeutic strategy for

such cases .

Overall survival was quite good at 86%

at 24 months and 80–86% at 48 months .

Stage was the strongest predictor of survival (P < 0.0005),

with 91 to 92% of patients presenting with stage I alive at 48 months .

cases who presented with stages III to IV in the literature survived 48 months after

diagnosis .

Despite aggressive approach to treatment this disease

pulmonary complications (50%) are the most common cause of death in patients who undergo surgery to the lungs for pulmonary metastasis