Fetopathology and developmental pathology of the embryo and fetus: Partial mole

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Partial mole

Etiology, pathogenesis

partial mole has a triploid DNA content: 69 XXX, 69 XXY
fertilization of a haploid egg by two haploid sperms
fertilization of a haploid egg by one diploid sperm (rarely)
the rate of maternal to paternal genetic information is 1 : 2.

Note: not all triplod gestations are partial moles — see chromosomal aberrations and fetal triploidy.

Macroscopic appearance

nothing remarkeble
malformed embryo is present and is aborted in the 1st trimester

Clinical signs

clinical presentation is that of missed abortion
hCG is slightly eleveted or within normal range for that time in pregnancy
therapy: evacuation of the mole, monitoring of hCG levels
prognosis:
- about 0.5 — 5% of patients with partial mole develop persisent gestational trophoblastic disease
- risk of development of choriocarcinoma following the partial mole is essentially nill

Histology

two populations of villi: swollen enlarged villi and normal small villi without edema
irregular scalloped villous shape, trophoblastic invaginations (fiords) and round trophoblastic stromal inclusions
focal trophoblastic hyperplasia
no trophoblastic atypia
blood vessels are present