Description

Gestational trophoblastic disease (GTD) is a group of rare conditions associated with pregnancy that consists of abnormal overgrowth of the placental trophoblast tissue. The most common condition is the hydatidiform mole which is often benign but may progress to an invasive mole or a malignant process such as choriocarcinoma (1).

• Hydatidiform mole: partial and complete (PM, CM)
• Choriocarcinoma
• Placental site trophoblastic tumor (PSTT)
• Epithelioid trophoblastic tumor (ETT)

Epidemiology

Incidence

• Difficult to assess due to limited data, rarity of disease and variations in reporting
• Declining incidence over the last 30 years in all populations (2)
• Hydatidiform mole: 2/1,000 in Asia, 1/1,000 in North America
• Choriocarcinoma: difficult to estimate, approximately 1 to 9 in 40,000

Prevalence
Limited data

Etiology and Pathophysiology

• All subtypes arise from abnormal proliferation of the placental trophoblastic tissue (1).
  • Cytotrophoblast: supplies syncytium with cells that become the chorionic villi covering the chorionic sac
  • Syncytiotrophoblast: produces human chorionic gonadotropin (hCG) and invades endometrial stroma for implantation
  • Intermediate trophoblast: located in the villi, implantation site and chorionic sac
• Hydatidiform mole:
  • PM: triploid (69XXX, 69XXY or 69XYY), chromosome from maternal and paternal origin; fetal parts present
  • CM: diploid 46XX, both chromosome from paternal origin; absent fetal parts
• Choriocarcinoma: malignant tumor with absent chorionic villi, abnormal syncytiotrophoblast, cytotrophoblast, necrosis and hemorrhage (2)
  • Most common type of gestational trophoblastic neoplasia (GTN)
• PSTT—abnormal mononuclear intermediate trophoblast on maternal side of placenta invading myometrium (2)
• ETT—abnormal chorionic-type intermediate trophoblastic surrounded by extensive necrosis and hyaline-like matrix (2)

Genetics
Mutations in NLRP7 and KHDC3L in recurrent molar pregnancy (1,2)

Risk Factors

• Hydatidiform mole
  • Extremes of maternal age: Risk of CM is 1.9 higher for women >35 years old, <21 years old, and 7.5 times higher for women >40 years old.
  • Prior molar pregnancy
  • Risk of repeat molar pregnancy is 1% or 10 to 20 times the risk of the general population.
• Choriocarcinoma
  • Prior CM (16–20%) or PM (0.5–1%) (3)
  • Asian and American Indian descent
  • Advanced maternal age
  • Possibly long-term contraceptive use and blood group A

General Prevention

No specific recommendations on prevention. Counsel those women with above risk factors.

Commonly Associated Conditions

GTN