Gestational trophoblastic disease

Gestational trophoblastic disease (GTD) results from the abnormal proliferation of trophoblastic tissue and encompasses a wide spectrum of diseases, including:

• hydatidiform mole
  • complete mole
  • partial mole
  • coexistent molar pregnancy
• gestational trophoblastic neoplasia (GTN)​
  • invasive mole ~10%
  • choriocarcinoma (gestational choriocarcinoma) ~1%
  • placental site trophoblastic tumor (PSTT)
  • epithelioid trophoblastic tumor (ETT)

Epidemiology

Women older than 40 years and younger than 20 years may be at higher risk.

Clinical presentation

The presentation is variable:

• uterus larger than pregnancy age
• abnormally high β-hCG
• hyperemesis
• hypertension
• theca-lutein cysts

Pathology

A common characteristic of all gestational trophoblastic disease is an abnormal proliferation of trophoblast, but different components predominate in different tumors.

Classification

• hydatidiform mole
  • complete hydatidiform mole (CHM)
    • commonest (up to 80%) manifestation of GTD
    • 46XX or 46XY: paternal chromosomes only
    • no fetus
    • β-hCG markedly elevated
    • atypia of cells present
    • treatment involves
      • curettage +/- hysterectomy in older women ¹¹
      • follow-up urinary β-hCG for 6-12 months
    • may progress to
      • invasive mole: ≈15% 
      • choriocarcinoma: ≈5%
  • partial hydatidiform mole (PHM)
    • 69XXX or 69XXY (paternal and maternal chromosomes)
    • may have a fetus or fetal components
    • β-hCG moderately elevated
    • no cellular atypia
• gestational trophoblastic neoplasia (GTN)​
  • invasive mole
    • distorts uterine zonal structures
    • boundaries between a tumor and myometrium are irregular and indistinct ³
    • may also invade parametrial tissue and blood vessels ⁴
  • gestational choriocarcinoma
    • may look identical to hydatidiform mole
    • arises following known molar pregnancy (50%), miscarriage (30%), normal pregnancy (20%)
    • can appear to have less vascularity than an invasive mole
    • higher β-hCG levels even than a complete mole
    • solid component with the visualized invasion
    • tends to invade myometrium through venous plexuses
      • patients often can present with multiple metastases without an easily identified primary, as it can often be small in an otherwise normal placenta
    • metastases can occur in
      • lungs: ~80%
      • vagina: ~30%
      • pelvis: 20% 
      • liver and brain: ~10% ^12,13
  • placental site trophoblastic tumor (PSTT)
    • rare form
    • produces small amounts of β-hCG
    • raise human placental lactogen (hPL) levels
  • epithelioid trophoblastic tumor (ETT) ⁹
    • extremely rare form