Hydatidiform Mole

Basics

Description

  • A gestational trophoblastic disease (GTD), which originates from the placenta and can locally invade the uterus and/or metastasize
  • Tumor arises from gestational rather than maternal tissue
  • Potential to develop into a malignancy:
    • Gestational trophoblastic neoplasia (GTN)
  • Complete mole:
    • Estimated in 1/1500 pregnancies
    • Fetal tissue not present
    • Diffuse chorionic villi swelling
    • Diffuse trophoblastic hyperplasia
    • Malignancy develops in 15–20%:
      • If metastasizes, usually to lung
    • Genetics:
      • Karyotype: 46XX (80%); 46XY (20%)
      • Paternal DNA expressed
      • Enucleate egg fertilized by 2 sperm or by a haploid sperm that duplicates
  • Partial mole:
    • Estimated in 1/750 pregnancies
    • Fetal or embryonic tissue often present
    • Focal chorionic villi swelling
    • Focal trophoblastic hyperplasia
    • Malignancy develops in 1–5%
    • Genetics:
      • Karyotype: 90% are triploid 69XXX, 69XXY, rarely 69XYY
      • Maternal and paternal DNA
      • Haploid ovum fertilized by 2 sperms or haploid ovum duplicates and is fertilized by normal sperm
  • Twinning with normal pregnancy possible with partial mole:
    • Higher risk for persistent maternal disease and metastasis
    • Possible to have normal infant

Etiology

  • Largely unknown
  • Risk factors:
    • Extremes of maternal age best estimated risk factor:
      • >35 yr old carries 2–7.5-fold risk
      • <15 yr old
    • Previous molar pregnancy carries 1–2% risk in future pregnancies (10–15 times the risk for general population)
    • Deficiency in animal fat and vitamin A
    • Smoking (>15 cigs/d)
    • Maternal blood type AB, A, or B
    • History of infertility and/or spontaneous abortions
  • Varies based on geography:
    • Asian countries have highest risk (2.0 per 1000 pregnancies)
    • US and Western Europe have lowest risk (0.57–1.1 per 1000 pregnancies)
    • Reported up to 1 per 12–500 live births in other countries
  • Finding in 1 of 600 therapeutic abortions
  • Not eliminated with use of Assisted Reproductive Technology (ART):
    • Risk of recurrence of molar pregnancy higher following ART

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